That is a very weighted question!! LOL!! I will give you the short answer.
As you develop your car will get more reliable but gearbox has reliability as one of the skill set that needs to be increased so I would focus on Gearbox reliability if you want to finish races.
On the development page you create a new design or Blue print and after it reaches 95-100% you will then need to click finished. Then the part is completed and can be produced on the production page.
As for the Max level reached I don't think I have seen; if you can explain where you see this?
I did a you tube beginners guide - quite long but might help. - once you get your head around this game it is pretty straight forward but there is so much to do as a new team so it does look quite daunting
Keep asking question as this game was built on the community helping each other understand the game and majority of manager are willing to share information that is needed.