@MrT10001 I am using Windows.
@beyolf Thank you for the advice. Now the installation worked. This is how I did it:
I let the installer run again until the installer stopped at "Rebooting to fastbootd". I manually updated two optional drivers in the Windows Update settings. They are called:
- LeMobile - Other hardware - Android Composite ADB Interface
- LeMobile - Other hardware - Android Bootloader Interface
After the installation of these two drivers finished the installation process finished automatically.
I don't know if both drivers were necessary or if one of them would have been enough.
Thank you for everyone who answered here.