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