No access to the settings?

I no longer have access to my settings. I'm looking for the settings, but can't find them anymore, eg: when I press the network settings, nothing is shown or happens (the settings window is not shown as if the settings are no longer on my PC or have been removed).

I installed MySQL database on my PC yesterday and then removed everything again (because it was not installed properly).

I have Linux as the operating system (Debian 10) and a Thinkpad laptop (intel CORE i7 (8th Gen)).

I will be very grateful if someone would help me.

1. What settings

The settings window where settings such as z.b. Bluetooth, audio, user account, network settings, etc. Stands) and there you can change (on-off, etc.).