I have played this game several times and never had this problem before. I am the 3 refus' and trying to find out who has the nucleic acid. He just keeps saying the same thing and there is never the 3 rufus' at the bottom to see who has the acid. so, I looked at a walkthrough and it says " After the dialog options are exhausted, click PPM of the left and right Rufus." What is PPM? I have waited thinking maybe sooner or later they would show up on the bottom so I could see that the right one has it but it never does. I even restarted from a save to see if there was a different option to answer, but, it was the same. Does anyone know what I am doing wrong? It worked before, but, I don't know what I did then. Thanks for any help!

I don't have a clue what PPM stands for. Usually I can figure stuff out like this from the context, but not this time.

Until someone comes along who has played the game, I would think there is probably a YouTube video walkthrough that could help you get through this part. Have you tried that avenue?

According to Google it refers to a pneumatic weapon.

If you submit to Google the question ..
“What does PPM mean in the game Goodbye Deponia “
You do get a sort of meaningful link to read.

I'm wondering what walkthrough you are using. Have you tried the one here at GameBoomers that MaG did? I don't see it using those letters PPM at all. Apparently the acid ends up in the sewer pipes and you change Rufus's to play different parts of the game. I have played this game but do not remember details at all.