Hi Terezija,
Have you tried holding Shift+Ctrl during the start-up in order to reset your frontend preferences, assuming that they may have gotten mangled up?
Compare:
https://reference.wolfram.com/language/tutorial/TroubleshootingTheWolframSystem.html
Otherwise please reach out to Wolfram Technical Support via
https://www.wolfram.com/support/contact/email/?topic=technical
and include your activation key, if you can, as well as any comments on how you may have customized or modified your Mathematica or Windows 10 recently.
Thank you,
Peter Fleck
Manager, Wolfram Technology Group