General Tip:
Play the game on tough difficulty from the start, it's not hard at all.
This way you'll guarantee a 100% Achievements completion in minimal time, there's a punch of tips on how to beat the "tough" difficulty below.

With that being said, let's start:

● Story Levels:
01. Out of the ice
Finish the first level

02. Yar har, fiddle di dee!
Finish the second level

03. Red Hawk Down
Finish the third level

04. Deep Sh*t
Finish the fourth level

05. Cavemen
Finish the fifth level

06. Headhunter
Finish the sixth level

07. Misplaced Luggage
Finish the seventh level

08. Think-Tank
Finish the eighth level

09. Da Bomb!
Finish the ninth level

10. Good enough
Finish the game at any difficulty

11. Fearless! (Hidden)
Watch the intro on "tough" difficulty

12. Call of War
Finish the game on "tough" difficulty
[It's not really tough, just make sure to:
¹' Use covers and shoot from it
²' Don't rush before knowing enemy positions
³' Always aim for the head]

● Weapons:
13. Son of the revolution
50 kills with AK47

14. US Grunt
50 kills with M16

15. Jerry
50 kills with UMP

16. Hillbilly
50 kills with M1014

17. Rocket Jumper
20 kills with M136
[At the 2nd Level when you need to bring down the helicopter, take the M136 rocket launcher and kill as many enemies as you can, then simply reload the checkpoint until you get the achievement]

18. Nebelwerfer
20 kills with grenades
[Pick up and use grenades every now and then and you'll get it in no time]

19. Arnie
50 kills with M249

20. Vasya
50 kills with SVD
[If you struggle with this one, just reload the checkpoint when you find it and kill enemies again, church at the 1st level is a good checkpoint for this]

21. Out of Ammo
20 kills with melee attacks.
[Melee key = F, easiest from behind]

22. Sharpshooter
50 headshot kills.
[Headshots system is bad but you'll get it easily]

● Add Ons:
23. Customizer!
Just Open the options Menu :D

24. Dumbass!
Kill yourself with your own grenade
[If you play on easy difficulty one grenade won't be enough, make sure to take some damage from enemies until you're close to death then blow yourself up :) ]

If that guide did help don't forget to leave a like and a comment on my profile, and if you have any questions i'll be in the comments to answer.

Cheers <3