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