This flight was the worst I ever experienced. It begun with taxiing to the runway, after a 2 hour delay. Even that was not smooth. I knew there were no winds, so I did not expect too many problems during take-off. Well, it took approximately 2 times normal time to take-off. During take-off, the plane went to the left, then to the right, not to make a turn, I am sure of that. I guess an inexperienced pilot or some other staff that brings you to another world. Also, the plane had very much trouble to get in the air. After 2 hours, we reached our cruise altitude! Forgot to say we were flying only 600 km p/h, according to the flight information, 850 is normal for a 737! Well, the plane might be overloaded? Service was also bad. I think this was a potential to crash.