Achievements Guideline

Some specifications for the hardest Achievement in the game:

First, don't restart a campaign each time you finish the game (as I did). When you finish the game, you can start a "new game +" (by pressing escape) which keeps the stuff you unlock, and let's you start over with the army color of your choice. If you start a new campaign each time, most of the achievements counter will be reset to 0 for
this new profile. But you still keep your stats on the first one.

Truckful of bullets : 100.000 bullets shot
You have to shoot all those bullets from the same profile. The deployable minigun, the one you install on the floor and press space to cease, doesn't count. You have to shoots all those bullets with a gun in your soldier hands. Elite Commando : Stab 10, kill 50 with a suppressed weapon and spot 15 strategical enemy structures
Same as before, keep the same profile, and you can continue this one in new game +. Elite tracker : Destroy 10 special crates and deliver 8 secret cargo vehicles.
Same as before, keep the same profile, and you can continue this one in new game + (you must even, because there is only 6 secret cargo vehicles by campaign, so you have to keep number 7 and 8 in new game+).
Even when you have conquer a map, you can freely explore for special crates and cargo vehicles. You can also navigate back to a map you have already left to get some special crate or vehicle if you miss some. Road devil: Roadkill 100 soldiers
Same as before, keep the same profile. But for this one, you can potentialy start a new campaign with 300% enemy spawning rate to increase the chances to roadkill. You've blown them away! : Kill 500 enemies with blast projectiles
Though the best way was to get 50 grenades on your backpack and go? It's not. Get some on your pockets just in case, but use a grenade launcher, it's way better. You can shoot on the other side of the screen with it. Give up already! : Died 500 times
Suicide counts. Freedom : Destroy 5 prison bus/doors
I'm not sure there is 5 prison/bus in one campaign. But as always, you can keep going in new game +. Expert weapon dealer
For this one, I kept 5 weapons of each type in my personal safe box. You can sell them to the armory as soon as you want, but this is easier to keep tracking of what weapons you need to collect. When you done collect 5 of 10 weapon types, be sure to not be in danger, find a personal safe box near an armory (or bring a mobile one to your personal safe box) and sell them all. Wreckage Master : Destroy 20 enemy vehicles
Any vehicles will do, jeeps are pretty common and only need one rocket to be destroy. Keep the same profile and finish in new game + if necessary.

Hope those tips will help some.

Greetings.