Why can't I press Maximize on the upper right?

Somehow it's only with Minecraft. I also always have to play in full screen mode. When I press F11 it just gets smaller again and I can't press maximize. The game starts by itself in full screen mode. I ask for help! I do not want to play in full screen mode anymore. This in the picture is not maximized and not a full screen!

Because you try it on the top right?

From an internet forum to such a problem:

In Windows search type "% appdata%" and press ENTER.
Open the ".minecraft" folder.
Open the local file "options.txt" with any editor, Word should also go.
Find the line "fullscreen = true". Change the "true" to "false" and save the whole.

https://www.gommehd.net/forum/threads/minecraft-nicht-mehr-maximieren-koennen.233795/

That's right…

You can show full screen in the options then the larger would have to go again