Resident Evil 6 Stuck in Leon's Campaign's Chapter 4 :/

[Don Quixote]

I am stuck in the plane mission where we have to open the hatch and keep the gas out. As the monster comes down through the roof of the plane's tail the mission starts. I quickly move towards the right side and press X on the hatch and then keep on pressing Square but as the bar reaches till the middle Leon dies because of the gas. On the next try i tried to shoot the monster in its feet and then quickly went towards the hatch but still in vain. I keep on dying due to that blue gas within 20 secs. Tried this mission again and again but failing. Cant get past it. Stuck in it. Can anyone help me out please? I shall be very thankful!

 

[Pancham Cutie]

The best way to get passed this part is to get the Leposita (Gas monster) to follow you to the back of the area or lure it to your partner and hope that it attacks your partner. Either way you'll have you to quickly hurry and open the box that has the lever inside to open the hatch. I think that it's also possible to stun the Leposita long enough to open the box, but I personally don't recommend it as it'll just be faster lure it either the back or your partner. It also sounds like you're going need more health if you're dying in 20 seconds, in that case you may want to restart the chapter and pick up the 3 herbs that are on the plane (One can be found in a small room on top of a chair, the second is in another small room on top of a table, and the third can be found right before you reach the cargo area right next to a Serpent Emblem and a case that holds 5,000 skill points.). There is also a First Aid Spray in the cargo area, but I don't recommend getting it until after you open the hatch since it's going to be right in front of the Leposita.