How do I regain control of my Firefox default search engine?

I downloaded PDFCreator24 earlier (uninstalled it long ago), this was probably the program that changed my search engine without asking, because suddenly it was Bing.

Then I deleted Bing, suddenly it's Google. If I delete Google and only Ecosia is in there (as it should), I try to search for something and it's Google again.

?

Which is also strange, at that time I had to somehow download an Ecosia add-on on this laptop in order to use it as the standard. With the previous laptop with the same operating system you worked fine without it? What's going on there?

https://de.malwarebytes.com/...dwcleaner/

Download, update once and then run through once. The program is specially designed to remove adware. Also look for weird addons and delete them.

And then: Go through all the settings again and set everything that doesn't look like your desired search engine correctly. The best thing to do is to clear the cache again. If necessary, reset the browser once.

And: Next time download programs from the original site and not from some dubious download site.

Thank-you. Yes, I saw above that Google was set as the default again, it always overwritten it. F! Ck Google!

Firefox is paid for by Google so Google is the default search engine when installing Firefox.

Yes, I've had the browser for months, it was always Ecosia