Think centered pop flick jump land every time u try a kickflip don't think kickflip think of the steps

Focus on being over the board and compress ur legs

Stay more above the board. Don't lean to foward or back just jump straight up.

I used to have the same problem, get your friend to film you in slow motion. then watch it over to see if your kicking down. it can feel like your sliding properly but sometimes at the last minute you end up kicking down

Focus in landing only with one foot, and so that many times until you get it right, then do the same thing with the other foot, and when you get it right, the other foot should follow