I am the owner of the unit. I bought years before the restaurant existed. It would definitely effect the price I got if I sold. Every night about 6 months of the year. The owner of the restaurant did pay for sound proof windows for my side of the building, but the difference is negligible.
I lived in a place like you describe. It was horrible. I know what you are going through. Eventually I moved though to somewhere quieter since I knew the place I was in was not going to change. Generally you have the right to quiet enjoyment of your home, however it may not apply depending on what your agreement says in it.
"You probably moved in there knowing this."
Really? From the OP:
"The Condo was built before the Restaurant."
And there was nothing to indicate the poster bought afterwards. As, it turns out, s/he did NOT.