Thank you boyo1991,
Yes, I had tried that, if I understand it right. Do you mean go to "on sd card" or to "Installed"? I assume, at "on sd card" the apps are already running on SD-Card (completely or partly), there is the option "Move to phone" or "Change to phone", but deactivated. When I go to "Installed" for some apps I find the option "Move to phone" (strange, they already seem to be on the phone, why is there this option?) and for some apps "Move to SD-Card", but this option is deactivated. E.g. Adobe Reader is shown twice on "On SD-Card" and on "Installed", why is that?
So, I cannot find a way to move apps from the phone to the SD-Card.