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