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