Hi everyone im an Amateur but i just a big question that would help a lot! I black the black side of the Italian game a lot and there are common themes that pop up and i do a lot of move that i think are good but am not sure. Could you please help? 

and a few other themes

in the second diagram

blasterdragon is correct. 6...Bb6 is a mistake and Bb4+ is better, the point being White will not be able to maintain his d4-e4 centre against correct play.

In the top one, you haven't made any gruesome errors, just a few second best moves. 5...a6 seems too early. 8...Bg4 seems illogical because the pin isn't as awkward as it might be with the f pawn still on f2, plus if you get your bishop driven back to g6, it looks like it will be a while before it sees much action again.

Marin considers 5...a6 most accurate, I don't fully understand why and it seems to transpose often.

EDIT: Tell a lie, wasn't paying attention, that's a slightly different position IIRC, when white plays c3, d3, and plays for the knight via d2, f1, g3 etc.

I think that the doubled pawns in the first diagram are good.  It opens up the f file for the rook, but it also allows white to play d4 and take back with the f pawn if black takes, thus unstacking them.

jphillips is correct. These are strong doubled pawns and help control the center as well as give White a nice file for his rook. 

This is why I don't like 5... a6 at all. Be3 is usually best met by Bb6, where Black can retake in the case of an exchange with axb6, opening up a nice file for his rook instead.