You can find out if your game has already been tested by searching by Title or CUSA number. If it exists but is not up to date, you can also update it.
You can also find out if your game is playable directly on the GUI.
Everything is indicated on the link.
Solve issues
You can participate by helping people with their issues.
There is also a Discord channel Help where you can give some help to newly people
How to Debug
We have a full guide to explain how to debug a game by yourself without programming skills
You can use it, it's very complete: Debugging guide