Lost against 2.Qh5

Today I lost a game while playing black against 2. Qh5 (1. e4 e5 2. Qh5).

Actually I did not respond correctly at some points. So I wanted to analyse the game. If you have some time, please point me with error prawn moves (and the reasons); so that I could come back strongly against this attack.

5. .. Nc6 wasn't a correct move. I would have chased away Queen by Bg5.

7. c3 - I could not understand this move. Does it has some importancy?

8. .. Rh7 - Seems this was a useless move to protect my Queen from a Queen exchange.

12. Bxc6 Bxc6 - Exchange a Bishop against a Knight at this point. But 'm not sure why my opponent choose to go for this exchange. ?? Any reasons?

16. In this move, opponent regain the lost Bishop by exchange. I could not find a way to avoid that.

Here f5 squire became unprotectable, and my opponent choose to place his Knight there which was a great threat towards me. But I had no good answer there as well.

Thanks for reading, but if you can help me in understanding my mistakes.