Hey guys, I finally made it work.
Obviously it was something really stupid: I needed to connect Rx WITH Rx and Tx WITH Tx.
I should have tried before, but it didn't make sense to me, because like Norbert said: Transmit should be connected to Receive. And all i found on the forum was confirming that. I didnt' know that sometimes it works the other way around.
By the way, thank you a lot for the support! You were very helpful!
Regards,
Edoardo