is there any device to make skis slower?

A skill makes them slower. The skill is turning uphill. Take a series of lessons from a qualified professional instructor. Your skis should glide easily when on snow so you can go across the hill instead of straight down it.

A slow ski makes it harder to ski. Hurts progress and can cause injury. Find a hill with lower grade.

There is actually wax that makes you go slower. Or you can just slow down whenever you need to.

Don't put wax on the bases. And if you really hate your skis, some low grit sandpaper would do the trick.

That would make me cry though so don't do that.

put sand paper on the bottom of them :)

for beginers