Firefox stubbornly wants to install itself instead of add-ons

For some months now I have not been able to install any add-on. When I want one, a page with the add-on appears, but the button links me unescapably to a download of whole firefox. Regardless of the fact that I click that link in FF already! Even if I try to install FF new, hoping the rest would appear automatically, the desired add-on keeps hidden.
I have Win 10 on a 64bit PC with FF 70.0. But this wrong link appears in Edge and Iron as well and has nothing to do with FF as such. Neither with my PC because till 4 weeks ago, I had the same problem on my old 32bit PC. I would add screenshots but it seems impossible here.

Did you change your user agent?

my husband who understands F12 fully found out that in the user agent there was a “anonymized by Abelssoft” remark. We googlefound here:
that this was an issue which could be removed by resetting the user agent, as described here:
I resetted as suggested, and it works fine!
Insofar, you have helped me with your user agent remark. Thank you