BUG #16740: Conflicting installations

The following bug has been logged on the website:

Bug reference: 16740
Logged by: jet2018
Email address: ezrajet9(at)gmail(dot)com
PostgreSQL version: 12.0
Operating system: Ubuntu 19.10
Description:

After following the guidelines on your documentation's installation, i have
faced a problem whose code is below:
1: I can't finish the installation. When I try on that I get this:

postgresql depends on postgresql-12; however:
Package postgresql-12 is not configured yet.

dpkg: error processing package postgresql (--configure):
dependency problems - leaving unconfigured
No apport report written because the error message indicates its a
followup error from a previous failure.
Errors were encountered while processing:
postgresql-client-11
postgresql-12
postgresql

E: Sub-process /usr/bin/dpkg returned an error code (1)

This does not only stop on the installation part, whenever I try to
uninstall this also it show the same. I thought it was a conflict maybe
between 12 and 11 versions, but now I cant remove any!!!

So the state am in is that I can't proceed or withdraw, what should I do?
I tried cleaning using
sudo apt-get autoclean
and it failed to solve the error

I tried forcing the installation using
sudo apt-get install -f

I surfed the whole of stack-overflow, it did not help too!!
SO WHAT DO I DO