Could you check on whether you have any unrecognized extensions? Disable ALL nonessential extensions on the following page, update your home page setting once again, restart Firefox, and see whether it sticks.

orange Firefox button or classic Tools menu > Add-ons > Extensions category

yes was 1st thing i did. had the another search site do the same thing once i disabled all of the extensions to make sure and didn't make a difference.

in this case also have a look for the user.js file & delete it as it's described in How to fix preferences that won't save.

afterwards you can use the search reset addon which will revert the most common changes those adware programs apply back to the firefox defaults.

That worked Thanks a lot to both of you for your help.