And what file you edited? In which folder?
In general, you aren't supposed to edit game files, you can make copy in the mod folder (one in AppData, %LOCALAPPDATA%\KillHouseGames\DoorKickers2\mods_upload\ , change the cost there, and enable mod, or it will be reverted back from time to time. You also need to have proper .mod file. The general instructions are availabe in the text file in the mod folder inside the game (not an AppData folder) alogside examples that can serve as templates.

Thanks for the fast reply
This is the Reddit link, I followed the steps the guys said:
https://www.reddit.com/r/doorkickers/comments/1atin63/how_to_change_unit_cost/

I checked the text file, and I feel like I'm gonna mess it up, so I don't want to try to be honest :D is there any way I can get the files I need from the web? I searched a lot but it seems like it's not a common thing to "cheat" this way. But I'd loooove to deploy more troops on some maps :D so yeah, sorry for being a pain in the arse, but can you maybe help me some way? :D

ChatGPT makes people unable to do basic stuff nowadays?

Listen, just download Notepad++ (or another advanced text editor what can help you with structure so it will make messing the files harder), install it, open the file in the "untis" folder that have "units.xml" in the name with it, then ctrl+f and search supply= in the opened window. You will see all the places where the cost is.

One supply point is 1/100 of "deployement point" cost.
"100"=1 deplyement point. Which is standard cost of most units in the base game.
"50"=1/2 deployement point. It's a standard cocst of N. SWAT expendables in the base game.
"25"=1/4 deployement point. Whcih means that you can deploy 4 units for 1 deployement point. At this point you aren't likely to have enough startpos aka "deployement slots" (circles where you place soldiers) on most map.
"20"=1/5 deployement point.
"10"=1/10 deployemnt points.

You can also change it in another direction, like make cost "200" and it will means that the deployement cost of the unit will be 2 deployement points.
And again, you can change it even for default game without creating mods in
\DoorKickers2\data\units\units.xml
but if there is any change to the file due to patches, or if you check file integrity you will lose the changes.

I don't use ChatGPT. You wrote exactly what I've done following the instructions from Reddit. And that didn't work for some reason. I meant I don't want to create any mod because I don't want to ruin anything in the game.

I changed every supply="100" to 50 and nothing happened, I still can't deploy more troops, one slot one person.

Ahhhhh I found half of the problem, it's one of the mods that mess it up, i think it's the project ARES.

Yeah it's gonna be that, I edited the units files, but didn't help. So I don't know what to do. Anyway thanks for the help, if you have maybe a soluton for the mods as well, I'd be glad to hear

Ares mod have it's own units. Editing the files in the game folder only affect them (N.SWAT, CIA and Rangers).
You need to edit _unit.xml file in workshop folder of ARES mod, but it will be rewritten even faster because ARES should get doctrines soon.