Sudden font problem

Hi,

at the website https://acesr.sk.data10.websupport.sk/ I got some sudden font trouble.

Symbols like “?, ?, ?” etc. are now not displaying correctly.

A week ago the site was working well, I made NO changes to .css, NO new posts, simply nothing new and the fonts are now displaying not correctly.

I tried to use several mysql backups that I made at the time site was working well, also tried to restore older WP files. Still no success.

I also removed some HTML issues (which did not harm the font before anyway).

Any suggestions please? I never experienced this kind of trouble since I am using wordpress (for many years)