Hi,
To help, we need to know more about your setup.
- What sort of HASS install are you using? (HASSOS, Core in a VM, etc)
- Is this a Mosquitto package installed directly on Debian? (the log reference to
systendsuggests YES) - Is this the HASS Mosquitto broker Add-In installed from within HASS?
Personally, I’ve run both a separate MQTT install and a HASS Add-In, and suggest the latter is easier to get working. You’re better off asking Debian forums for a standalone install - there’s a lot in the config file to get wrong.
I’d also suggest not posting screenshots (they are a pain to read), and use test with code fences instead.
Here’s a walk through of MQTT installation and configuration for HASS:
If this helps, 
this post!