Hi the upgrades from scrap can only be done on parts that have stars near the top of their picture. So you can upgrade these parts 3 times but it takes a lot of scrap to do this and you only gain a small increase to their monetary value. Also only scrapping parts worth 1cr gives lowest return. Just noticed you have the body repair table (in middle of workshop behind engine stand) you can repair parts and body when they are above 15%.
