Is there a feature on this software or site, where I can use it to randomly bring questions and tests in lessons i have completed to test my knowledge?

Hi Rigoletto, 

Unfortunately we don't have any feature that would allow you to create your own tests, if this is what you would like to do, I'm sorry; I will forward the message as feedback though, to our Product Development team for consideration. 

Cheers!
 

Thanks Maria.

it would be good if there is that feature that it can pick out random parts of lessons randomly to test myself.

Buona giornata