First, we'll need the Steel Division 2 Modding Assets.

After you download them, head into:
...\Steam\SteamApps\common\Steel Division 2\Mods
and click onto CreateNewMod.bat
there you'll need to write a name for your mod. You can use anything, like TEST for example.

After that, it will create a new folder (if you called it TEST, then TEST) in ...\Steam\SteamApps\common\Steel Division 2\Mods
Open this folder, there you will need to go into:
...\Steam\SteamApps\common\Steel Division 2\Mods\TEST\GameData\Gameplay\Gfx
and find CadavreConstantes.ndf
open it (you can use notepad)

Here, we have few things:

export CadavreInvulnerablePeriode is 1 * Seconde - I'm not sure what this does, don't change it. Just to be sure we don't break anything.

// Temps de vie total = CadavrePeriodEnFeu + Cadavre_Duration_Apres_Feu
// export CadavrePeriodEnFeu is 120 * Seconde - how long burning wrecks of vehicles stay on fire, as you can judge by the "//" and the fact that there's a duplicate right underneath, this one is not being used, but you can edit both just to be sure.
export CadavrePeriodEnFeu is 300 * Seconde - same as the previous thing, but this one is being used.
export CadavreDurationApresFeu is 3000 * Seconde - how long vehicle wrecks (after they stop burning) stay on the battlefield.

// Temps de vie total = CadavrePeriodEnFeu + Cadavre_Duration_Apres_Feu
export CadavrePeriodEnFeu_Batiment is 120 * Seconde - how long burning buildings stay on fire (I think this is for the defense buildings, like MG nests)
export CadavreDurationApresFeu_Batiment is 3000 * Seconde - how long destroyed buildings (after they stop burning) stay on the battlefield.

// Dans le cas de l'infanterie on a pas de cadavre en feu donc :
export CadavreDuration_Infanterie is 10 * Seconde - and finally, how long the corpses of dead infantry units stay on the battlefield.

After you're done, save & close the CadavreConstantes.ndf and head into:
...\Steam\SteamApps\common\Steel Division 2\Mods\TEST\GameData\Generated\Gameplay\Gfx
and open DistrictsCadavreDescriptor.ndf
press CTRL + F and search for CadavreDuration
there should be 3 values of
CadavreDuration = 10*3600
Edit this to the same value that you put for CadavreDuration_Infanterie in CadavreConstantes.ndf, but leave the *3600 at the end.
Don't forget to edit all the 3 values.
Save DistrictsCadavreDescriptor.ndf and close.

Now, head back into ...\Steam\SteamApps\common\Steel Division 2\Mods\TEST (or other name of your mod)
and click on GenerateMod.bat
It can take a while. If you wait for 3-4 minutes and nothing happens, try to ALT + TAB.
It should say that your mod was successfully generated.

Now, launch the game, click onto MOD CENTER, find your mod (TEST, if you named it like that) and check the box under ACTIVE.
Click APPLY and you're done.
You can test if it works in skirmish.