Hello! Thanks for the answer. I here to mention few things. I've tried game resource viewer before i make this thread and it do only one helpful thing - presents a list of files inside which all empty(0 B). Next i've tried godot unpacker with renaming RPA archive into PCK. There i met a little success - dragon unpacker give me 10 objects(out of... more than 10) which finally mean something but nothing more than black squares(oh, there's a cross!..and the hardest file is big in question of dimension but that picture isn't just black square). Also via game resource viewer i can check expansion and most of files is WEBP instead of PNG. Maybe that's an issue?
Good job shopping around. Some devs don't want people looking at their files so hard they modify the file format (they swap where size and offset are stored I think but doesn't look like that's what happened here). As far as I remember webp doesn't cause problems. If the game name is known it'd be possible to take a look.
Ok, sorry for make you waiting. If you wanna check it out so here it is: https://disk.yandex.ru/d/fjAhNSOCL0LVKg