You and your opponent agreed to this 15days/move. If you want it to end quickly just resign.
My friend is deliberately trying to stall on online chess.

:0 did a mod remove my post? are there really mods on here? HEY MODS GO TO TOPIC "What is the best opening for white?" AND LOOK AT SOLIPSIST's POSTS THERE!!! PLEASE!
kco is right: you agreed to the terms when you accepted the game. If you want to play faster, start another game with someone else.

WHY did you agree to 15 days/move unless you expected there would be multiple periods approaching 14 days between moves?
When I played ICCF international postal chess in the 1970's, the Cold War was on and postcards between me and some players in Eastern Europe's Iron Curtain Nations took a month to get back and forth. I stopped playing ICCF after the round of games that took me so long.
My friend made a online chess game where you take 15 days to move. I don't know if i can do anything about it, but it is seriously bugging me. He may be really sad that i won against him 5 times, but on the last day he makes a move. This game would probably take a year. Can i somehow abort this game under certain conditions? I wonder if stalling is just plain mean or its ok... If i am an active player this is troubling...