my texture mod for "lies of p" doesn't work and game crashes

[Yanthereski]

(this is the first time im making mod for UE4 game)

i follow step by step making unreal engine mods tutorial on youtube : 

1-i used "unreal mod unlocker" and steam less

2-i used AES.Key.Finder and got the pak file keys 

3- with umodel i extracted the game pak files 

4- i edited one texture with photoshop and saved it as .tga format

5-i used the same virsion of unreal engine as the game then cooked my edited file in to .uasset and i paid attention to the file path as well and replaced it in correct path

but game crashes in loading screen .

so i downloaded another texture mod from the nexusmod and placed it in the same path to find out if the problem is with my path. but that mod worked correctly

the only difference i found between my mod and the one i downloaded from nexusmod is that my file is in .uasset format but the other mod has 3 files in it with .uasset and .ubulk and .uex p format

and every where i search i cant find out 1-what these files actually are?

2-do i need them for creating my mod?

3-how can i create them ?