Why did he slide on the ground ? This has been happening to me every other run since yesterday and I can't explain why. When he slide, i can't move or jump in any direction until he decides to stop. Does it happen to anyone else?

Given I've never seen or heard of other, similar reports... it's almost certainly an issue on your end. And based around the idea that you're having dropped inputs... first thought would be a keyboard issue. Have you noticed similar dropped inputs when playing other games or using your keyboard in other situations?

You could also try playing the game on a different site. Or via a different browser. To see if that might help? Might be some kind of intermittent lag spike, caused by who knows what on your computer.

Its been a while since i last played but iirc theres a bug with that specific platform only where because of its heigh you can jump into this slide as you call it where you wont be able to jump for a few sec. It used to happen to me frustratingly often and the fix was to double jump to get up there to reduce the chance of it happening. I think i asked about it on the discord when i first came across it, so you could do that aswell