hello, could you go to the firefox menu ≡ > help ? > troubleshooting information, copy the contents of that page and paste them here into a reply on the forum? this might give us a clue what is going on...

Hello elvynaa, philipp

probably the hardware acceleration is the problem, try disabling graphics hardware acceleration, and see if that is the cause of the issue.

You might need to restart Firefox in order for this to take effect, so save all work first (e.g., mail you are composing, online documents you're editing, etc.).

Then perform these steps:

1. Open Firefox Options tab as follows, click the menu button and select Options .
2. In the Firefox Options tab, click Advanced, then select General.
3. In the settings list, you should find the Use hardware acceleration when available checkbox. Uncheck this checkbox.
4. Now, restart Firefox and see if the problems persist.

Thank you.