I assume because the home partition has still luks encryption. On startup the first thing I get is a gnome rescue screen and some new, cryptic name for an encrypted partition.
I will try to delete the encrypted partition, merge it with the partition where now the new manjaro is on an install it on this merged space.
I hope I don’t mess up. I read a bit about how deleting luks encrypted partition in the first place. No noob stuff 
well dont know nothing above encryption issues, but did you use the same username and same password when you were reinstalling?
I unlocked the root partition to be able to install manjaro on it with the installation program on the usb live seesion. But maybe I didn’t unlock the home partition. I also wonder how to make the new manjaro accept the existing home partition, but thought I’ll just have to try. And see what happens.
So I merged the parititons with gparted, then installed manjaro and at the end got an errorcode 1, saying the bootloader couldn’t be installed…
Here’s the log:
http://termbin.com/no6y
well it looks like it wants to install grub for bios/mbr:
Target cmd: ("grub-install", "--target=i386-pc", "--recheck", "--force", "/dev/nvme0n1") Exit code: 1 output:
Installing for i386-pc platform.
grub-install: warning: this GPT partition label contains no BIOS Boot Partition; embedding won't be possible.
grub-install: error: embedding is not possible, but this is required for RAID and LVM install.
2023-01-12 - 09:06:34 [2]: WARNING: [PYTHON JOB]: "Command 'grub-install --target=i386-pc --recheck --force /dev/nvme0n1' returned non-zero exit status 1."
2023-01-12 - 09:06:34 [6]: [PYTHON JOB]: "stdout:Installing for i386-pc platform.\ngrub-install: warning: this GPT partition label contains no BIOS Boot Partition; embedding won't be possible.\ngrub-install: error: embedding is not possible, but this is required for RAID and LVM install."
boot the iso in uefi mode and that should do it
Do you mean botting the live usb in uefi mode and then reinstall?
yes thats what i mean
Sorry but I have to ask – do you mean turning legacy mode and secure boot off?
(When I boot into Windows it says it’s in UEFI Mode.)
I didn’t follow the whole thread but you must turn off Secure Boot for Manjaro.
Actually I meant the contrary:
@brahma
What exactly do you mean with UEFI mode.
Legacy rom mode off and secure boot on
@mithrial
I have secure boot off, but my question was in the context of reinstalling manjaro and because of an error message brahma suggested to “boot the iso in uefi mode”
He gives you something to eat. But you have to chew yourself. 
Okay, Guess I missed the point where I’m out of questions 
Thanks guys. I’ll try on my own!
this is what i mean:
I took another look at my bios and if it’s about being set to uefi instead of legacy, then it already is set to uefi.
just read what you wrote here:
and do it!!!
you were booting he live usb in legacy/bios mode, which the logs here indicate:
so just boot the USB in uefi mode… it has nothing to do with bios…
Have u turned off Fast Startup inside windows?
If not then turn it off. I am assuming u hv a SSD.
Inside windows the option for fastboot isn’t visible, seems to be a thing that can happen.
As I had Manjaro running succesfully and think to remember meeting all the basic requirements before, I don’t think this should be an issue.
In Bios there is a fastboot setting where I can choose betwenn minimal, thorough and auto.
When I power up the pc I press F12 to get to a menu. It says that the system is in UEFI mode and secure boot is off.
When I use ls /sys/firmware/efi I get no such file or directory, which means that the system is in bios mode, if this article is correct: How to Check if Your Computer Uses UEFI or BIOS [in both Linux and Windows]
So currently I don’t get it.
PS
No need to respond though, I’ll try something following this guide:
Sorry for bothering you so much.
you are in uefi, the logs from the failed install are clear…
and you cant boot into your installation, so ls /sys/firmware/efi is output from the live usb, which according to the logs is booted in bios/legacy mode…
dont follow any guide, just boot the usb in uefi mode and install, and thats it…
when you boot the usb you have a option to boot it in uefi, so select it and thats it…
if you are not sure take a picture of the boot options where you select to boot from the usb
Thanks for pointing that out once more. I was blind 
It made me realize that in the start up screen my usb drive isn’t listed under UEFI boot options, but only under legacy mode options, which explains a lot.
I tried to figure out a way to add it to the uefi list in my bios, reading in a Dell forum.
However it seems that in the related section of the bios I can’t add it. There’s an option to add new devices to the UEFI list, but it seems that the USB drive isn’t listed there, so I can’t choose it. I’m pretty sure about it. When I tried adding the only partition/drive that looks exactly like the content on the USB Drive, it turned out to be my new and flawed installation of Manjaro.
(I think so, because it starts with the same error with which my machine starts since the failed installation. There’s an error that says that the encrypted drive XYZ is not found, and a grub rescue command-line. I guess this is just because I activated encryption for the new Manjaro and the installation wasn’t successful)