Player jump Higher at low fps(jump isn't framerate-independent)

Hello, i make a flappy bird copy and the character jump higher at low fps and higher at high fps.
I make an custom gravity by removing value from player velocity every frame( i don’t know if this is the correct method
to do this but, it works)

To make the player jump i add force then the player press space


This is an comparasion between the jumps in different fps.

Also try to avoid the mistakes, english is not my native language