Hello @EHHVTC I MartinCZ
If you are playing the game at high settings, it is normal for the file size to be high. When you lower your graphics settings and take a new screenshot, you'll notice that your file size has decreased. However, if there is no noticeable change in the file size when you look at it, you can benefit from a different screenshot taking application, steam or the button to take screenshots on your keyboard.
Best regards,
kelt_kreqht