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