Dual Screen in full screen on mac

I got a problem on my dual screen setup : On the second screen, Resolve can't be in full screen even if the main screen is. And the second screen doesn't take up the full height. Can you help me ?

What is the resolution of the second display? Do both displays have identical resolution?

No they are different, the main is 2336x1510 the second one is 1920/1080, the aspect ration of the main display affect the second one, can I change this setting like a windows with border ?

Thanks in advance

Is the second display set to Extended or Mirrored in macOS Settings > Displays?

It's set to Extended!