All information about modding.

Hello, forum users! I'm new to modding and have a question. I'm planning to change several terrain and factory textures for the Stronghold faction. I used Total Commander to view the archive, data.pak. I found the texture I needed, for example, a single gray stone. I modified it in Paint DDS, without making any major changes, essentially just recoloring it. I saved it in the same format, and Total Commander packed it back in. After that, the game stopped launching. As a result, I concluded that when I make changes to this archive, the game stops launching for me, and reverting the changes fixes the issue. What did I do wrong? The problem is obviously at the repacking stage...