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