please help with genesis graphics editing

[DarkPig]

Hi hackers

I just fully translated the game "Beauty and the Beast : Belle's Quest" to french. I had no problem with texts, as well as adding infinite lives, but I am stuck with graphics...

I want to replace the original english title screen :

with this one I made, a french title screen using the same color palette as the original :


I tried many tile editors, but tiles always look altered, just "mushy pixels". I searched and learned that many game graphics are compressed... But I don't find how to uncompress it.

Here is what most of the file looks like :


Sprite tiles are clear though, here I see the character's dress :


By the way, here is what the VDP debugger shows me while this screen :


Or maybe it would be easier to add it in the rom's empty space and tell the game to display it instead of the original ? I don't know how to do that neither.

Please help me, my translation just needs this screen to be finished.