Hey! I’m trying a bunch of linux distros, and i’m liking Manjaro, but I want to put my NVIDIA GPU to work instead of my integraded graphics of CPU. Does somebody knows how I switch between GPUs?
And, another problem is my second monitor not working (LG 1080p HDMI 75hz)
Welcome to the forum! 
You need optimus-manager, and since you’re on Plasma, you probably also want optimus-manager-plasma and plasma5-applets-optimus-gpu-switcher.
I’m afraid I cannot help you with that, but quite possibly it may start working once you’ve enabled your Nvidia GPU.
Thank you very much for replying me, but, how do I get those things you told me to get?
They are all in the repository. 
sudo pacman-mirrors -f && sudo pacman -Syu optimus-manager optimus-manager-plasma plasma5-applets-optimus-gpu-switcher
Be sure to let it finish, because it can take some time. It’ll first select the up-to-date mirrors and rank them in terms of network performance, and then it’ll run a full system update — there was a major Stable Update again early this morning.
By the way, that last package is a widget that you can add to your panel.
Note: I do not know whether optimus-manager will be sufficient. You probably also need an Nvidia driver, but I don’t have any Nvidia hardware and therefore I cannot offer you any advice on that. There is however a pertinent section on Nvidia at the Arch Wiki.
OK thanks!
The code finished with the following error: error: unresolvable package conflicts detected
error: failed to prepare transaction (conflicting dependencies)
:: optimus-manager and envycontrol are in conflict
How do I fix it?
and when I ran optimus-manager appears this error: ERROR: a GPU setup was initiated but Xorg post-start hook did not run.
Log at /var/log/optimus-manager/switch/switch-20231201T152834.log
If your login manager is GDM, make sure to follow those instructions:
If your display manager is neither GDM, SDDM nor LightDM, or if you don’t use one, read the wiki:
Cannot execute command because of previous errors.
Hmm… I didn’t know you had envycontrol installed. I know that it’s somewhat similar to optimus-manager, but like I said, I have no experience with it. The Arch Wiki recommends optimus-manager, so I would advise going with that, and removing envycontrol.
Best would be to break it down into separate steps then. Make sure your mirrors are up to date (if you haven’t already done that) and update your system with…
sudo pacman -Syu
Then remove envycontrol and install the optimus-manager stuff.
sudo pacman -R envycontrol && sudo pacman -S optimus-manager optimus-manager-plasma plasma5-applets-optimus-gpu-switcher
You can only install one at a time. Pick one.
the command to remove envycontrol says that it didnt found envycontrol lol
And I didnt instal envycontrol that I remember
Then how can they be in conflict? 
It may have come on the ISO you installed from, or maybe it was installed as a dependency for some other package. 
the error given was: error: target not found: envycontrol
Try installing those packages again and paste the output here verbatim. Type two rows of three backticks each and paste your output in between the two rows.
what packages? This one? sudo pacman -R envycontrol && sudo pacman -S optimus-manager optimus-manager-plasma plasma5-applets-optimus-gpu-switcher
This. 
warning: optimus-manager-1.5-3 is up to date -- reinstalling
resolving dependencies...
looking for conflicting packages...
error: unresolvable package conflicts detected
error: failed to prepare transaction (conflicting dependencies)
:: optimus-manager and envycontrol are in conflict
What is the output of…
pacman -Qi envycontrol
…?
error: package 'envycontrol' was not found
Then your package database is corrupt. Try running a check on it first, and then download a new package database…
sudo pacman -Dkk && sudo pacman -Fyy
error: missing 'java-runtime=19' dependency for 'java-atk-wrapper-openjdk'
error: missing 'youtube-dl' dependency for 'persepolis'
I’m guessing that you’ve got a bunch of old/outdated AUR software installed, and possibly that you haven’t updated your system in a long time.
youtube-dl is an AUR package, but as best I know, it is deprecated and it is now advisable to use yt-dlp instead. java-runtime is neither in the repositories nor in the AUR.
I would advise you to uninstall java-atk-wrapper-openjdk and persepolis. You can reinstall them again later if you want.
sudo pacman -R java-atk-wrapper-openjdk persepolis
The above won’t fix your envycontrol problem. But take care of the above first and then we’ll take it from there.
I installed today lol
error: target not found: java-atk-wrapper-openjdk
error: target not found: persepolis