Permalinks won't change

I have the following (and rather frustrating issue):

I created a simple site: coming-soon.glücksmacher.ch with a menu of three pages.
As many times as I have tried to change the permalinks to ‘post name’ nothing ever happens. In fact, I have tried to change the permalinks to any possible setup under the permalinks page but the actual url for each page doesnt change.

Example: currently the page url appears as
https://coming-soon.gluecksmacher.ch/?menu=social

and all I want to do is remove the ‘?menu=’ but so it reads
https://coming-soon.gluecksmacher.ch/social

I’ve checked each page’s permalink seperately and they are correct. But using permalinks settings won(t change anything. In fact, any setting that I’ve tried the url remains the same.

It’s driving me crazy, to say the least.

Anyone knows what I can do to have this resolved?

Many thanks in advance!!
Konstantinos