I think I know what is the problem:-)
Instead using wifi6/ac or ax my rpi has wifi4/n.
I read that changing the countrycode to „BO“ will fix this issue.
As I’m using OSMC on my rpi4 I do not have anymore the raspi-config to change wifi settings or the country code. When I go into the osmc menue → rpi menue there i See only very few config options.
I know that the country code can be changed in the wpa supplicant file but in my directory there is no such file?!? Why?? Shal I just create it manually??? I have connected my device over the osmc wifi menue just for your information.