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