Yes, it is possible: as patrickbider says below, charging happens at slightly reduced power/speed. Instead of "super fast charging" with "fast charging" on my Galaxy S21 FE.

You can charge the mobile and power bank at the same time. In this case, however, the mobile is charged with reduced power.

No! I tried, but it does'nt work.
No! I tried, but it doesn't work.
There is no hint in the instructions.

No idea. Defective appliance returned to seller