install Mozilla Firefox app on mac

Dear people,

I am trying to install Mozilla Firefox on my Mac. That is not a problem so far and the app works fine. But every time my Mac updates and / or reboots, Mozilla Firefox has disappeared again ....... The whole app cannot be found and I have to reinstall.

Does anyone have a solution for this problem for me?

It can't be that Apple decides for me whether I use Firefox or not? That's absurd!

Thanks so far, greetings Peter