[Ghazban]

Raise the flop. Slowplaying straights on two-flush boards is very bad. With all those broadways out, you'll probably get some action from a good ace or something like pair+gutshot (AQ/AT/KQ/KT/QJ/JT).

Since you didn't raise the flop, raise the turn. If villain has the flush, he'll probably let you know. If you raise the turn, get called, and get checked to on the river, you can either value bet or check behind depending on if you read villain to be the type to semibluff flop, call turn, and try to checkraise the river with a flush.

Raising the river is bad. You have plenty of showdown value but nothing you beat can call a raise except a horrible player with trip kings.