High CPU usage at Fortnite?

I have the following problem with Fortnite:
My CPU usage is at 100%, Fortnite alone has 80%.
I capped my game to 240 frames per second but every now and then my Discord packs up and so on.
I have already activated all 6 cores.
Specs:
CPU: i5 - 8500
GPU: 1080

At what resolution do you play?

1920x1080
Doesn't matter

I have no lags

It does matter (but the resolution shouldn't be a problem) and how much RAM do you have?

16 GB

Edit.
games 1798x1080