iMac stucks on 100% in boot

Hello everyone,

I have in the moment a serious problem with my 2017 iMac running MacOS Catalina BETA. After a normal reboot the iMac loaded until the bar reached 100%. Then for hours nothing happens, it just stays at 100%. 

The things I tried:

• Boot in Safemode - still hangs on 100%, can’t access Safemode
• Reset NVRAM/PRAM - nothing happened 
• Reset SMC - nothing happened 
• Run First Aid on all disks - helped and discovered nothing
• Uninstalled Google Chrome update in terminal - nothing happened
• Tried to reinstall MacOS Catalina - not enough space on my disk 
• Tried these commands: cd /Volumes/Macintosh\ HD/var/db/caches/opendirectory and mv ./mbr_cache ./mbr_cache-old - “no such file or directory”
• Tried to boot in startup manager - still hung on 100%
• Tried to run the Apple diagnostics - it said everything is fine
• Single user mode with commands like mount-uw / - command not found
• Let the iMac sit for a couple days - still hangs on 100%

And so on...

So, as you can see, I tried many things and nothing helped. Do you have a good solution or a advice/suggestion without erasing the disk? I would REALLY appreciate a good and quick answer!

Thank you and I love to hear from you,

Aaron