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