I can’t edit link properties and I can’t start text mode

I am using the latest version of WP and Google Chrome. I am using the classic post editor. I can insert a link. I can bring up the link address box but I cannot edit the properties including opening the link in a new tab. After clicking on the edit link icon, the vertical scroll bar of the screen disappears. It reappears only after reloading the page. I can’t start text mode either. My errors from the Google Chrome console:

Uncaught ReferenceError: kopa_variable is not defined
at HTMLDocument.<anonymous> (script.js:362)
at i (jquery.js:2)
at Object.fireWith [as resolveWith] (jquery.js:2)
at Function.ready (jquery.js:2)
at HTMLDocument.J (jquery.js:2)
/favicon.ico:1 Failed to load resource: the server responded with a status of 404 (Not Found)
wplink.min.js:2 Uncaught TypeError: Cannot read property ‘show’ of undefined
at Object.open (wplink.min.js:2)
at i.onclick (plugin.min.js?wp-mce-49100-20200624:1)
at mp.c.fire (tinymce.min.js:2)
at i.fire (theme.min.js?wp-mce-49100-20200624:1)
at HTMLDivElement.o (theme.min.js?wp-mce-49100-20200624:1)
at C (tinymce.min.js:2)
at HTMLDivElement.d (tinymce.min.js:2)

The page I need help with: [log in to see the link]