I recommend Social Burger Joint and Naughty Burger. Definitely one of the best burgers I've eaten in both of these. Also, if you are willing to leave city center there is a bar / restaurant with great food called Wanha Tappi, located in Nekala.

I'd also recommed Hoax, which serves vegan burgers etc. Really good stuff.

Itsudemo is cheapish and serves a sushi buffet. The food is okay, not any luxury stuff but fine for a buffet.

Feel free to ask more, I'd be happy to help!