Yes, LH738's Sachsenhausen is O.K. but somewhat touristy, however, inexpensive.
A good area is "Fressgasse" near Alte Oper: Rest. "Leiter" or "Gallo Nero" ...
Or "Erno's Bistro" nearby. All are somewhat expensive but worth the price ...
If you like food, go to "Klein-Markt-Halle", between Roemer and Hauptwache.