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