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