hm. somewhat reminds me of some other (old) games where windows has problems with displaying them fullscreen on high-dpi-monitors.
translating myself from a German interface (windows 11) :
A RMB click on the exe, choose properties -> compatability tab, click the
"change high-dpi settings" button, tick the bottom option ("
dismiss high dpi scaling"), choose "
application", OK, OK.
if that does not help, simply repeat but unchoose that "
dismiss high dpi scaling" option -> all is as it was before.