To get achievements: go to time mode and spam the down key for the entire time limit, as it's the fastest way to score high and get money. Purchase "life rescue" in the shop and if you still can't beat the hard badge go back to the time mode and earn enough to get "time slowdown" in the shop. From there, it's up to your skill to get the hard badge, I've helped you all I can.
@AlexNeb That... that's what you do... Garbage (and engineer!) trucks are vehicles, you build those to complete level 7. A bit weird to think of people riding garbage trucks from city to city during the (super energy) apocalypse, I agree, but adding something to the game that you only used in one level and had no real purpose wouldn't really make much sense.
 "Feed the King"){kind=icon}
 "Super Energy Apocalypse : RECYCLED!"){kind=icon}