Help on car tire slip and net Force!

I am working on a semi realistic car system .As it is a raycasting chassis i have to simulate all the forces by myself , i’ve found a way to simulate the lateral friction and it works fine for now but for the longitudinal Force ,i’ve struggled on it ,i’ve spent more than a week searching and trying different things but still didn’t manage to make it happen.

My questions are:
is the net Force coming from the slip or is the slip a by-product?
Why there isn’t enough information about the net force moving the car and about the traction force ?

Feel Free to leave a comment or a suggestion if you don’t have the answer And Thank you for helping me out.