Kumusta,
The default display scaling feature on Windows 10 or further is a core component of Windows OS. But sometimes this feature for some specific apps can cause compatibility issues, unreadable texts, blurry signs, and ultimately app crashes. source: thegeekpage.
And I faced a problem with this Windows DPI feature too, especially when I'm in gaming mode (RF Online).
This screenshot says it all:

Print Screen
on the keyboard to screenshot in-game in RF OnlineHow to solve it?
It's easy, you need to disable High DPI settings for individual apps.
Step 1: Find a main .exe on your application (in RF Online, it's RF.exe)
Step 2: Right-click on that .exe, and then open Properties.
Step 3: when the Properties pop-up opened, click on Compatibility tab

Step 4: on the Compatibility tab, click on Change high DPI Settings and check Override high DPI scaling behavior. Scaling performed by: Applications. Click OK.

and then Restart the application.
Exclude Application Display Scaling in Windows 10 problem solved! 😉
New screenshot:

Thank you for reading, Paalam.