hello, can you try to replicate this behaviour when you launch firefox in safe mode once? if not, maybe an addon is interfering here...

Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems

Thank you Phillipp but I have no addons at all. I am experimenting with all kinds of Linux distros like Linux-lite, ubuntu, etc and I get the same problem on all of them. I remember I had the same problem last year on windows 7 and solved it by editing the config file but unable to find the same post nor I remember what I did to fix it... :-(

hi, actually it doesn't clear the text for me as well - however it highlights the whole text, so that when you start typing it just gets overwritten...

Yes, that is the normal behaviour but when I start typing in the search or address bar, it does not clear what was there before....

OK, I found it searching the about:config database. The problem was that browser.urlbar.clickSelects.All was set to "false". I changed it to "true" and now is all fine....

Also to fix the same problem with the search bar, I changed browser.search.context.loadInBackground from false to true.