Remind me of a custom platform movement I did before the corresponding behavior was created.
Did you do that as an exercise?
You should use dt to ensure smooth and non fps-dependant movement.
add 50*dt to xSpeed will add 50 per seconds but bit by bits every tick ('cause dt is the time between two ticks)
And then set X to player.X + xSpeed*dt you will go at xSpeed px/seconds
Also as Weishaupt said it's better if you provide the capx, there's some other information we need to judge your work or at least to try it.