Alright,first of all thank you for the thread.
Turkish television has had a lot of great movies. In Comedy we had
Vizontele and
Organize Isler movies. Cem Yilmaz and Yilmaz Erdogan are (who were both actors in those movies i mentioned) arguably two of the best actors and directors/producers.
As for "underground" scene,I'm not sure which director i can suggest,really. However,if you're interested,there's a crime movie coming up named
Cingoz Recai . It's adapted from the book with the same name. To keep it short: It's about an evil-genius-criminal trying to run away from a genius cop (Like Arsene Lupin against Sherlock Holmes) and in the meantime seducing all the ladies.
To learn about the culture,I don't think I can give you anyone other than Fatih Akin. He is a Turkish-German director who makes movies with pieces from both cultures. In July is what I'd suggest you to watch.
Cheers.