More alive than the living.

Yeah, I somehow missed your message.

I completed it on "Hero" difficulty, or the map is easy, or I didn't understand something.

It's easy, yes. I'm preparing a new, more difficult version.

It feels like there's a passage to the remaining part of the map somewhere, but I couldn't find it.

No, it's just a plot device: the map has a continuation.

I didn't hear any voice acting in the scenes (meaning speech in Russian or another language), only some kind of panting and sound effects...

I just downloaded the archive, and there's some kind of chaos inside: apparently, the final version was packed incorrectly. I'm suggesting this: I'll try to speed up my work on completely redoing the map from scratch; there won't be any problems there. However, I won't be doing voice acting: it takes up a lot of space, and the quality leaves much to be desired: I didn't graduate from a theater school ;)