header problems

Hello, I’m following a tutorial on youtube (Ferdy Korpershoek) on making the website with Astra. He is very clear and it is all very understandable.
But some little changes for some reason do not seem to work when I try them and I start to think if there is maybe a bug in my theme?

F.e.: I want to change the mobile header so that it is stacked. But when I make this change, it is also changed for the other displays, not just for mobile.

And: It seems impossible for me to enter text or a button on the header image. The raster frame that would show in the tutorial, is not there when I hover over my image. What could be the problem here?

Hope to hear from you!