Multiple instances of one application is installed

Hi guys. On my system it’s like several instances of the same app installed. Some was different languages so that is sorted out. Can someone help me with this thing thou, how to list all installed apps, and so I have a clean system not a messy one with lots of versions etc. or same instances., Please, I need to find out exactly what apps are on my system. Meanwhile I will try to read the manual for apt-get. Thanks

Probably related to Two apps/icons of many applications

For managing .deb/APT packages you may use synaptic.

For listing installed snap, in a terminal
snap list
To remove a snap
sudo snap remove app_name