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