In Windows 10 - Task Bar search for Advanced System Settings, it will open and you’ll see a Performance button, which will open up the Performance Options, select the Advanced Tab, it will show Virtual Memory section and a Change… button, click on that
Don’t let windows manage it, if you’ve only got one HD, make it as big as possible and grab a shovel and see if you can dig up another drive from the backyard.
I once picked up a HP server from a rubbish pile, with 3 good and 1 bad, 2TB WD Green Hard Drives in it.
If you have more than 1, remove the paging file from the Hard Drive with Windows and/or Fortnite on it for better performance.
The minimum recommended size for UEFN is 64Gb