Help with SFML Collision and Gravity

This is my first attempt with SFML and game development, and I'm having issues with the collision and gravity.

I'm making a 2D platformer game using a tilemap system.

Collision seems to be working(slightly) but is very choppy, the characters jumps about to random places and its just not ideal -_- I just can't seem to get gravity to work properly. I've tried a few different tutorials but I cant get anything working and I'm at a bit of a loss right now.

If someone could point out what I'm missing here it …