Cotaks
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3
gravity is a b*tch 
add some force() +z to it 9.8 is default gravity so 9.8 will counter the sliding
when in air add some force() to -z to let it drop faster
move the player with velocity (if using bricks) then if you put y = 0.1 the speed will not go faster but a dash can be activated to push you forwards.
If you know python a bit, give this a try