I'm italian, then sorry form my poor english

I have downloaded "opencart_v0.7.8.zip" and installed it.
Then I have downloaded "New_Paypal_Improved_v079.2.zip", extracted it, and copied it into the root of my opencart site.
In administration section of my site, I went in "extension --> payment" and I selected "new"; I insert this field:
* Code: paypal
* Directory: payment
* Filename: paypal.php
* Controller: payment_paypal
then I enabled this extension.
If I try to configure this extension, appears this error:
Fatal error: Call to undefined method Request::gethtml() in /var/www/html/opencart/admin/controller/payment_paypal.php on line 274
what is this error??
the version of the paypal extension is correct?
Please, someone could explain me simply how to configure correctly this extension?
thaks!