Cannot boot anymore on Dell Inspiron 7706 2-in-1 after Update from Windows 10 to Windows 11

Hello

My Dell Inspiron 7706 2-in-1 suggested to update to Win 11 yesterday. I did so. After the installation process, the system does not boot anymore. It shows the Dell logo and then the waiting logo keeps spinning forever. I had about 3 hours of chat with a Dell supporter via WhatsApp. After a lot of hints and ideas which I followed precicely, I had to give up.

In this process I also  tried to re-install a new version of Windows 10 by creating an installation media stick. Even a completely new installation failed. The ssd cannot be detected by the installation tool. I also added drivers (according to advice from support) to the installation stick. But in vain. What can I do? Any other ideas?

Is it possible to install Windows 11 manually? But I haven't take a note from my Windows licencse number. I copied nearly everything except this licence id.

I fear I have to send in my laptop to Dell service to get it back to work again. Any idea helps.

Best regards,

Frank