Hello Giannis_19, welcome to the Microsoft community, I'll be happy to help you today;
I understand that you are having problems playing Fortnite on Windows 10;
What platform did you download the game on? Stem, Epic Games or Xbox?
What exactly is the error message displayed? (if possible send a screenshot of the error);
What exactly is the model and manufacturer of your video card?
Before answering the questions above I suggest that you make sure you are up to date with the latest version of Windows 10;
Press Windows key + i and go to Update and Security;
Click Check for updates and do ALL pending updates;
Update Microsoft Store apps;
Open the store and click on Library;
Click on Get updates and wait for all apps to be updated;
run a disk cleanup;
Press Windows key + R and type: cleanmgr press Enter;
Click on clean system files and wait for the files to load;
Select all files and click ok to delete them;
Perform a clean boot;
Press together the keys: Ctrl + Shift + Esc to access the task manager;
Click on start and disable all programs that start with Windows;
Restart the PC and check if the problem persists;
Hope this helps, see you soon!