If I click on File - Export, the program crashes.

Please post your System Information as Lightroom Classic (LrC) reports it. In LrC click on Help, then System Info, then Copy. Paste that information into a reply. Please present all information from first line down to and including Plug-in Info. Info after Plug-in info can be cut as that is just so much dead space to us non-Techs.

First thing I would try is resetting the preference file. https://www.lightroomqueen.com/how-do-i-reset-lightrooms-preferences/

If that doesn't help, try turning off the Graphics Processor in LrC: Preferences->Performance->Use Graphics Processor set to OFF

What program are you talking about? What version NUMBER?

What operating system are you using? What version NUMBER?