ubuntu 18: PostgreSQL does not start. how can I totally remove and reinstall it

Hi there

I made somehow a mess with my PostgreSQL installation an an ubuntu 18.4 with 
PostgreSQL 10.0

service postgresql status
● postgresql.service - PostgreSQL RDBMS
    Loaded: loaded (/lib/systemd/system/postgresql.service; enabled; vendor 
preset: enabled)
    Active: active (exited) since Sat 2021-01-23 21:21:13 CET; 2min 26s ago
   Process: 1853 ExecStart=/bin/true (code=exited, status=0/SUCCESS)
  Main PID: 1853 (code=exited, status=0/SUCCESS)

I would like to remove everything, and reinstall.

How can I do that?

It seems, that

apt remove --purge postgresql
apt remove --purge postgresql-client

I not enough, as I have the same situation afterwards.

Or is there a way that I can rebuild PostgreSQL datastructure?

thanks

Robert