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