I had fortnite on my PS4 but I uninstalled it a while back. I started playing on my nintendo switch and wanted to link the progress from the ps4, but it says that the ps4 account is linked to another epic account. how can i just unlink that epic account and link it to the one i have now?
It is not epic account that is linked it your console account that is linked and Epic account is one that containing game data, so linking Playstation account won’t transfer data from Epic account you made back then. You would need unlink Nintendo account and log in to old Epic count from Playstation and link Nintedo. But it goes 2 ways, you wont get content you gain on Switch.
You might try to email account support they might help you out more. Also please don’t post Fortnite questions here as this site is dedicated exclusively for UE4 development, it’s even less likely for oyu to get any Fortnite answer here. I only answered question only because i had it on top of my head ;]