Battleye for Fortnite?

I get when I start Fortnite on the PC that BattleEye can't be installed.

what can I do to install BattleEye for Fortnite on the PC and if so where can I download it?

BattleEye is not mandatory to play Fortnite on PC. This is just an additional piece of software designed to prevent cheating / intervention by other programs in Fortnite's files.

And what can I do now

Specify your question.

Well there says install BattleEye failed and that every time I start Fortnite I have already uninstalled everything

And now the question is what should I do if I should download BattleEye somewhere or how?

Hope your english is good enough: https://www.partitionwizard.com/partitionmagic/failed-to-install-battleye-service.html

That's working?

Try it.