Here is the full list of all 46 Car Mechanic Simulator 2021 achievements. It takes around 120-150 hours to unlock all of the achievements on Windows.
Renovate and sell 50 cars
Finish 100 orders
Unscrew 10 000 bolts
Finish path test 25 times
Paint 60 cars
Reach level 50
Unlock all upgrades
Fix 150 body parts
Finish all the special missions
Unlock 10 parking alleys
Fix 50 body parts
Sell 1000 parts from inventory
Buy 3000 parts from main shop
Reach level 20
Finish lap with time under 1:50
Buy 25 cars from impact cars
Visit Barn 30 times
Balance 50 tires
Fix 150 car parts
Buy new car in car salon
Buy 5 cars from impact cars
Paint 5 cars
Swap engine
Reach level 3 of garage expansion
Earn 2000 scrap parts
Buy 30 cars from barn
Earn 500 scrap parts
Buy 30 cars from junkyard
Renovate and sell 1 car
Fix 50 car parts
Buy 1 car from barn
Earn 50 000 CR on sell cars
Earn 5000 CR on sell cars
Buy 1 car from junkyard
Visit Barn first time
Balance 5 tires
Finish path test first time
Finish order with money bonus
Reach level 5
Visit a junkyard
Buy 100 parts from main shop
Pour old oil on the floor
Visit Salon
Finish order with experience bonus
Finish test track
Finish 1 order