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