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