Well, you need a softmodded wii for this, so I'm just going to assume you do have one. It's actually pretty simple, just use Riivolution to replace the game's files with the new ones.
Well I have Riivolution on my Wii but I do not have the original game files I hope it's okay.
I tried to do it my way i'll see if it works.
Also, is it okay if my language is French or I need to put my Wii on english to make it works?
I don't think you're understanding how Riivolution works.
You don't need the original game files on the SD card, just the disc. Riivolution scans for the "new" game files on the SD card and temporarily patches the game disc so that it uses the new files instead.
Every game needs a game definition; it tells riivolution many things, including what game disc is in the console, and the directory where it checks for the new files.
Uh, okay... Try placing this in the riivolution folder, and launching riivolution. Place the new files in a folder on the root of the SD card called "mp9"(exact lowercase letters and without quotes)