Hi Koray,
I see your problem, the reason for it is because in editor x, master sections, (such as your header), have separate breakpoints from the pages, you can see that when you are focused on your header the breakpoint icons turn to green. If you want to make changes across more breakpoints in master sections you need to add these breakpoints for your masters (the green ones).
I would also recommend reading up on Masters in the Academy X site here’s a link: