1° I was using manjaro gnome since the 17 release in UEFI mode and every time i tried to turn off the laptop, the screen was frozzing for a while (10-20seconds) before answering my call. In Legacy mode it does not occurs
2° My keyboard has retro illumination and in KDE the menu that controls it works fine but in gnome the same menu does not works. In both cases the keyboard shortcut to control it works fine too.
Not sure what you mean with UEFI and Legacy mode. Is there somewhere a switch that you can simple toggle between them?
As far as I know, you should have installed your system based on your hardware. If your MB supports Legacy mode, then your system needs to be installed that way or you are asking for problems.
Here was just posted few hours ago a gentle reminder how to ask for help, please read it, then provide all the info relevant to your problem, so someone could help you. for example in your case, what is your BIOS based on, UEFI or Legacy? You are member here from May, you probably know all this
Ah, now that you are providing more info, it makes more sense. Did you check the logs for errors? (journalctl, Xorg.0.log...) Are there any? If so, could you post them here. Do you need a help locating the log files?
Hope someone can help you. Try to provide as much useful info as possible though