Nothing works after the upgrade

I dont understand,..why do we need to re-upload everything in order to upgrade? Why OC can't make it easy, just replace a file or security patch??? Just Upgraded from 2.1 to 3.0.2.0, and nothing is working, all site collapsed. All the permissions are correct(tried for 3days to fix using every given scenario)This is from the front:
Notice: Use of undefined constant DIR_STORAGE - assumed 'DIR_STORAGE' in /home/xxxxx/public_html/system/startup.php on line 70
Warning: fopen(DIR_STORAGElogs/error.log): failed to open stream: No such file or directory in /home/xxxxx/public_html/system/library/log.php on line 22
Warning: Cannot modify header information - headers already sent by (output started at /home/xxxxx/public_html/system/startup.php:70) in /home/xxxxx/public_html/system/framework.php on line 108
Warning: fwrite() expects parameter 1 to be resource, boolean given in /home/xxxxxx/public_html/system/library/log.php on line 31
Warning: fopen(DIR_STORAGElogs/openbay.log): failed to open stream: No such file or directory in /home/xxxxx/public_html/system/library/log.php on line 22
Warning: fwrite() expects parameter 1 to be resource, boolean given in /home/xxxxx/public_html/system/library/log.php on line 31
Warning: fopen(DIR_STORAGElogs/openbay.log): failed to open stream: No such file or directory in /home/xxxxx/public_html/system/library/log.php on line 22
Warning: fwrite() expects para
This is from admin:
home/xxxx/public_html/system/startup.php on line 70
Warning: Cannot modify header information - headers already sent by (output started at /home/xxxxx/public_html/system/startup.php:70) in /home/xxxxx/public_html/system/framework.php on line 108Notice: Use of undefined constant DIR_STORAGE - assumed 'DIR_STORAGE' in /home/xxxxx/public_html/admin/controller/startup/sass.php
Also, tried to upgrade Journal theme per instructions, at the same time. Didn't work, re-uploaded just OC files again, got "successful" upgrade msg., but with all these errors...
Please advise. Thanks

I dont understand,..why do we need to re-upload everything in order to upgrade?

Well, that's only, because you don't understand the Concept. In Contrary to Microsoft,
Opencart does not change the Version Name, like XP, Vista, WIN-7, e.t.c., only the Numbers.

And not a single Win User would ever try, to i.E. upgrade a Win-7 to WIN-10, by simply
overwriting an existing Win-7 on a hard Disk, and then still expect everything to work as before.

If such would be the Case, then, it would not need a new Software, a few files would be sufficient,
but since OC does not employ a few hundreds of Coders, and since OC does not charge for the
Software itself either, one would sure not expect, to receive all this, in Windows-like Style, possibly
even by automatic Installation, for free !?

But OC would also not have created a new Version, if everything would function and work as before.
Just like a new Windows, one cannot use any Win-7 Prog. DLL in a Win-10, and one cannot use an
older Version Theme, or Extension, if one changes from any other Version up to latest OC v.3.x , take
it as a fact, or then, go back to the Version, you used before.

At least, if you still have a clean Backup of the old DB, otherwise, you really screwed up, by NOT
coming here before, to find out about first ...

But this would only be your Problem too ...
Good Luck !
Ernie

Thanks, ...you have really been very helpful!!! Have worked with dozen's of shopping carts before..and other software updates, nothing like that ever happened..and yes, it is possible headache-free upgrades..I'm not sure which planet you live on?.. but, you're right...OC sucks..

Well, why then coming to OC, if other Shopping Carts work so well ?
Nobody forced you to, and if you cannot handle it, it's nobody else's problem.
Good Luck!
Ernie