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