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