Simulating a vehicle in a realistic way is a difficult topic. There are several different complex aspects you need to simulate correctly and put together in a coherent way. So it's understandable that actual authors will provide little help. It's like if you ask “hey, I want to make games in Unity but I can't, please someone tell me how to make games in Unity”.

My recommendation is to either use a ready-to-use vehicle physics package from the Asset Store, or just forget about vehicle physics at all and use a regular CharacterController with vehicle-like movement rules (i.e. rotation rate depending on the speed).

There are alternate clever solutions like using just ball physics:
https://twitter.com/Nitroneers/status/1238779466832363520

I provide two vehicle physics packages in the Unity Asset Store: Edy's Vehicle Physics for arcade-style vehicles, and Vehicle Physics Pro for realistic vehicle physics. Still, I recommend you to check out the vehicle packages available in the Asset Store and choose the one that best fit in your specific project. Every package uses different approaches and provides different features and integration levels.