I cannot move guides, neither on sample pages nor on document pages.
The guides ar neither fixed nor placed on a different layer.
Restarting the program didn't help either nor restart of my Mac.
What can I do?
I opened your file from the links posted above.
I see a number of locked objects on page 2 when I expand the layer in the panel. No doubt this is why you cannot select them. You can change this behavior by going to the General section of the preferences and unchecking the box for Prevent Selection of Locked Objects in the Object Editing section. This will allow you select and edit locked objects, but not move or delete them. To do that they must be unlocked, which you can do in the Layers panel.
#Peter Spier, thanks a lot again! All my problems solved for today (until now 😉 Now I've gotten to know InDesign much better.
To delete the horizontal guides on the Parent pages -
Layout > Create Guides > Remove Existing Ruler Guides.
#Derek Cross, thank you, I checked that before (further up in the thread). No positive results.
#Barb Binder, thank you, I checked that, no positive results.