view cart http error 500

Hi to everybody here in the forum.
I write to you because I have a big problem that I try to solve without success.
My version of opencart is 2.0.2.0 and I have bougth a few extension without problem and all worked good.
But in two different day I bought 2 extension from opencart.com and I had the same problem: I installed it in ocmod and then my cart was disabled and I saw a blank page with this error

http error 500

I hope that you can help me to solve this problem!!!
thank you very much to everybody and best regards

In your admin - > systems - > tools - > error logs, what do you notice on the latest error messages reported for the cart page?

If you do not see any related errors, ensure to have enabled the error logs from your admin - > systems - > settings - > edit store - > server - > Log Errors - > Yes.

Thank you for your reply straighlight!!!

This is the log but the problem is that I asked to my hosting to backup my site to the previous version of the site before the error

2016-03-24 22:15:11 - PHP Unknown: mysql_connect(): The mysql extension is deprecated and will be removed in the future: use mysqli or PDO instead in /home/pjkafqgw/public_html/system/modification/catalog/view/theme/default/template/common/footer.tpl on line 106
2016-03-24 22:15:11 - PHP Unknown: mysql_connect(): The mysql extension is deprecated and will be removed in the future: use mysqli or PDO instead in /home/pjkafqgw/public_html/system/modification/catalog/view/theme/default/template/common/footer.tpl on line 106
2016-03-24 22:15:11 - PHP Unknown: mysql_connect(): The mysql extension is deprecated and will be removed in the future: use mysqli or PDO instead in /home/pjkafqgw/public_html/system/modification/catalog/view/theme/default/template/common/footer.tpl on line 106
2016-03-24 22:28:41 - PHP Notice: Undefined variable: connection in /home/pjkafqgw/public_html/system/modification/catalog/view/theme/default/template/common/footer.tpl on line 106
2016-03-24 22:28:41 - PHP Warning: mysqli_query() expects parameter 1 to be mysqli, null given in /home/pjkafqgw/public_html/system/modification/catalog/view/theme/default/template/common/footer.tpl on line 106
2016-03-24 22:28:41 - PHP Notice: Undefined variable: connection in /home/pjkafqgw/public_html/system/modification/catalog/view/theme/default/template/common/footer.tpl on line 106
2016-03-24 22:28:41 - PHP Warning: mysqli_error() expects parameter 1 to be mysqli, null given in /home/pjkafqgw/public_html/system/modification/catalog/view/theme/default/template/common/footer.tpl on line 106
2016-04-07 19:50:33 - PHP Notice: Undefined index: fsp_match in /home/pjkafqgw/public_html/system/modification/catalog/controller/checkout/cart.php on line 391
2016-04-07 19:50:44 - PHP Notice: Undefined variable: ip in /home/pjkafqgw/public_html/system/modification/catalog/view/theme/default/template/common/footer.tpl on line 127
2016-04-07 19:50:45 - PHP Notice: Use of undefined constant free_geo_zone_id - assumed 'free_geo_zone_id' in /home/pjkafqgw/public_html/system/modification/catalog/model/shipping/free.php on line 7
2016-04-07 19:50:50 - PHP Notice: Undefined index: teaser_status in /home/pjkafqgw/public_html/system/modification/catalog/controller/checkout/cart.php on line 39
2016-04-07 19:50:50 - PHP Notice: Undefined index: teaser_status in /home/pjkafqgw/public_html/system/modification/catalog/view/theme/default/template/checkout/cart.tpl on line 38
2016-05-17 17:05:27 - PHP Notice: Trying to get property of non-object in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 442
2016-05-17 17:07:43 - PHP Notice: Trying to get property of non-object in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 442
2016-05-17 17:09:18 - PHP Notice: Trying to get property of non-object in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 442
2016-05-17 17:10:21 - PHP Notice: Trying to get property of non-object in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 442
2016-05-17 17:15:42 - PHP Notice: Trying to get property of non-object in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 442
2016-05-17 17:16:26 - PHP Notice: Trying to get property of non-object in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 442
2016-05-17 17:16:30 - PHP Notice: Trying to get property of non-object in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 442
2016-05-17 17:30:48 - PHP Notice: Trying to get property of non-object in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 442
2016-05-17 17:45:31 - PHP Notice: Trying to get property of non-object in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 442
2016-05-17 17:58:14 - PHP Notice: Trying to get property of non-object in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 442
2016-05-17 18:29:01 - PHP Warning: DOMDocument::loadXML(): Opening and ending tag mismatch: modification line 3 and file in Entity, line: 32 in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 434
2016-05-17 18:29:01 - PHP Warning: DOMDocument::loadXML(): Extra content at the end of the document in Entity, line: 33 in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 434
2016-05-17 18:29:01 - PHP Notice: Trying to get property of non-object in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 442
2016-05-17 18:29:09 - PHP Warning: DOMDocument::loadXML(): Opening and ending tag mismatch: modification line 3 and file in Entity, line: 32 in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 434
2016-05-17 18:29:09 - PHP Warning: DOMDocument::loadXML(): Extra content at the end of the document in Entity, line: 33 in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 434
2016-05-17 18:29:09 - PHP Notice: Trying to get property of non-object in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 442
2016-05-17 18:29:43 - PHP Warning: DOMDocument::loadXML(): CData section not finished

<ul id="social">
<li><div><a href="#" onclic in Entity, line: 63 in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 434
2016-05-17 18:29:43 - PHP Warning: DOMDocument::loadXML(): Premature end of data in tag add line 59 in Entity, line: 63 in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 434
2016-05-17 18:29:43 - PHP Warning: DOMDocument::loadXML(): Premature end of data in tag operation line 56 in Entity, line: 63 in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 434
2016-05-17 18:29:43 - PHP Warning: DOMDocument::loadXML(): Premature end of data in tag file line 41 in Entity, line: 63 in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 434
2016-05-17 18:29:43 - PHP Warning: DOMDocument::loadXML(): Premature end of data in tag modification line 3 in Entity, line: 63 in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 434
2016-05-17 18:29:43 - PHP Notice: Trying to get property of non-object in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 442
2016-05-17 18:30:30 - PHP Notice: Trying to get property of non-object in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 442
2016-05-17 18:30:36 - PHP Notice: Trying to get property of non-object in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 442
2016-05-17 18:31:45 - PHP Notice: Trying to get property of non-object in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 442
2016-05-17 18:32:56 - PHP Notice: Trying to get property of non-object in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 442
2016-05-17 18:34:35 - PHP Notice: Trying to get property of non-object in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 442
2016-05-17 18:36:24 - PHP Notice: Trying to get property of non-object in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 442
2016-05-17 18:49:42 - PHP Warning: DOMDocument::loadXML(): Entity 'themeFolder' not defined in Entity, line: 31 in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 434
2016-05-17 18:49:42 - PHP Warning: DOMDocument::loadXML(): Entity 'themeFolder' not defined in Entity, line: 41 in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 434
2016-05-17 18:49:42 - PHP Notice: Trying to get property of non-object in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 442
2016-05-17 18:50:16 - PHP Notice: Trying to get property of non-object in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 442
2016-05-17 18:50:22 - PHP Notice: Trying to get property of non-object in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 442
2016-05-17 18:50:57 - PHP Notice: Trying to get property of non-object in /home/pjkafqgw/public_html/admin/controller/extension/modification.php on line 442
2016-05-18 21:49:57 - PHP Notice: Error: E-Mail to required! in /home/pjkafqgw/public_html/system/library/mail.php on line 61
2016-05-18 21:50:48 - PHP Notice: Error: E-Mail to required! in /home/pjkafqgw/public_html/system/library/mail.php on line 61
2016-05-18 21:51:55 - PHP Notice: Error: E-Mail to required! in /home/pjkafqgw/public_html/system/library/mail.php on line 61
2016-05-18 21:52:31 - PHP Notice: Error: E-Mail to required! in /home/pjkafqgw/public_html/system/library/mail.php on line 61
2016-05-18 21:56:43 - PHP Notice: Error: E-Mail to required! in /home/pjkafqgw/public_html/system/library/mail.php on line 61
2016-05-18 21:58:05 - PHP Notice: Error: E-Mail to required! in /home/pjkafqgw/public_html/system/library/mail.php on line 61
2016-05-18 22:00:56 - PHP Notice: Error: E-Mail to required! in /home/pjkafqgw/public_html/system/library/mail.php on line 61
2016-05-25 22:11:45 - PHP Notice: Undefined variable: name in /home/pjkafqgw/public_html/system/modification/catalog/view/theme/default/template/common/footer.tpl on line 67
2016-05-25 22:13:34 - PHP Notice: Undefined variable: name in /home/pjkafqgw/public_html/system/modification/catalog/view/theme/default/template/common/footer.tpl on line 67
2016-05-25 22:13:37 - PHP Notice: Undefined variable: name in /home/pjkafqgw/public_html/system/modification/catalog/view/theme/default/template/common/footer.tpl on line 67
2016-05-25 22:16:19 - PHP Notice: Undefined variable: name in /home/pjkafqgw/public_html/system/modification/catalog/view/theme/default/template/common/footer.tpl on line 67

In both config.php file,

you need to change:
to:
Take note that most error fields reported on the above are not core fields. They rather come from installed contributions. First, see if changing the DB_DRIVER info will mostly resolved the issue.

Thanks straightlight

I checked the two config.php...the first in the root and the second in the admin dir...

and it is already correct

define('DB_DRIVER', 'mysqli');