Device did not show up after 30 seconds... (I can't install manjaro)

this appears after selecting “boot with open source drivers”:

Starting version 251.4-1-manjaro
ERROR: /dev/disk/by-label/MANJARO_KDE_2137’ device did not show up after 30 seconds…
Falling back to interactive prompt
You can try to fix the problem manually, log out when you are finished
sh: can’t acces tty: job control turned off
[rootfs ]#

Means here:

Unplug your boot device, plug it in, wait a few seconds and run exit. It should boot. No idea, but on some hardware it is buggy.

what do you mean when you say ‘run exit’ ?

Ok…
[irony]
look at your keyboard. There are so called “keys” which you can press and gives you an output on the screen. Type slowly e x i t and then ENTER (I hope you find that button).
[/irony]

Type exit and type enter. Then you run exit.

It works, after a few seconds the mouse appears but now the problem is that the whole screen is black (but I can move the mouse), even I waited 10 minutes but it still the same.

At that point switch to another TTY:

Shortcut: CTRL + ALT + F1 - F7

There you should be able to login as
user: manjaro
password: manjaro
(Don’t forget to press ENTER)

When you are logged in, you can view some logs:

journalctl -b0 -u display-manager

Ultimately you can restart the display-manager (in other terms the login manager)

sudo systemctl restart display-manager

If that does not help. Then start you desktop environment directly:

# stop the display-manager
sudo systemctl stop display-manager
# For gnome for example:
startx /usr/bin/gnome-session

However… if such a problem happen then it is most likely a gpu problem of some sort. Since I have no information what so ever about your system, you are on your own.

When I press ctrl + Alt + f7 and I wait, it shows:
[Ok] Finished initialize Pacman keyring
[Ok] Remached Target Multi-User System
[Ok] Reached Target Graphical interface

But I can’t do or type anything

Then, I press ctrl + Alt + F1 and I can see the mouse and black background.

How do I type those things that you say?

F1 - F7F1 or F2 or F3 or F4 or F5 or F6 or F7

On F3 you should get a login prompt.