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