Seeking Restaurant Recomendations in Frankfurt

Hello,

I will be visiting Frankfurt/ Germany for the very first time and will be in town on a Monday evening and all day Tuesday in August, I wanted to ask for recommendations on delicious non-touristy places to eat. Am especially looking for places open on Monday night.

Also, if you can recommend a nice cocktail bar that will be lovely, someplace you would actually hang out.

Cheers,
Latha
Dallas, Texas, USA