Sometimes it feels really long before Christmas is here
I have been busy and out of the house, therefore I was not able to post this earlier.

Thank you Inger – I just could look into it with SD- and it is woorking great. However only in preview Firefox – not with preview SD.

I feel a little bit unhappy with Franks solution because for me as a non coder the construction cannot really be understood. Because of not understanding JS and the font icon . For example I have to use the main container “wrapper" for the full page – I cannot seperate content and Nav ? I tried but all became confused. A second main wrapper beneath the Nav wrapper cannot be controlled – at least by me. It is invisible...
But I still have to test a little bit. And look, if Wayan’s solution will be better to handle for me... Until now it seems to be … Let's see.

Correction -
"A second main wrapper beneath the Nav wrapper cannot be controlled – at least by me. It is invisible..."

Now it works