I’m afraid we do not offer Windows support here, but if you need help with your Manjaro system then you are going to have to provide us with more information than “it won’t start”. That tells us nothing ─ see the post I linked to above.
For starters, you’re going to have to switch off Secure Boot in the UEFI firmware settings. Manjaro does not support Secure Boot. Also switch off Fast Boot if enabled.
I have installed Windows 10. Then I installed Manjaro, everything ran top. After that I wanted to install windows 11. Now I get the message: error: unkonow filesystem. entering rescue mode …
grub rescue>_
Just a hint: Most likely Windows Setup is not able to mount the EFI Partition and install the Windows Bootloader Files, because it cannot find it. There is a Setup log on the Windows Partition, which should confirm this. You need to mount the efi partition with diskpart, remove the windows folder and reinstall the bootloader with bcdboot. There are hundreds of tutorials on the web.