Disable auto-brightness when the video is in full screen?

I Fixed it (Windows 10). If you’re on a Laptop, there’s a configuration in the Display settings you should take a look. In the “Brightness and color” that says “Change brightness for built-in display”, turn it to 100% then adjust the brightness manually in the keyboard while running a fullscreen video (usually a sun icon in the F11 using Fn key), after that the brightness stayed the same on any app.