editing links: issues with the behaviour of the input box

Dear forum,
Having already looked for a remedy a few times without any success, I feel compelled to bother the pros: when I try to edit an existing link and cklick on the pen in order to fix the link in the input field, a lot of weired things happen regularly which cost a lot of time. One of my common tasks is to transfer HTML links from a certain source to WordPress links. To do this I very often have to remove the characters “.htm#” and replace them with “/#”, also a “/” has to be put at the beginning of the link. When I click on “htm” to remove these three characters as a start and then try to continue with the “#” and the “.” and jump to the beginning of the box, in the meantime suggestions pop up underneath which lead to the entire box beeing shifted (mostly) upwards (and sometimes being reshifted somewhere else) and the next clicks or characters being misinterpreted:
– sometimes the “htm” is reinserted
– sometimes the “\” lands at the end instead of the beginning
– sometimes a new WordPress page is being generated.
So often I have to finish the entire action, press Ctrl-Z and start anew.
The effect seems to depend on the speed of typing and clicking. Although I’m not the slowest typer under the sun, I often do not manage to escape the misbehaviour by being quick enough. Can I please, as a beginning, get rid of these – regularly useless – sugestions ??

The system is always the latest update of Windows 10, WP 6.0.2 with Gutenberg as standard, but the behaviour existed in 5.* already. 2014 theme – but that should be irrelevant.

Thanks in advance for any clues to the apprehension of the perpetrator(s)
Stefan

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