Ah I totally forgot about it :D Yes that helped me to get unstucked, but like you said take away the investigation part.
Making a good detective game is really really hard because you have to balance this, the player should not find the solution to fast so he get bored or to slow so he get frustrated. Then you have different player some that are good in such games and some are bad. There is a good video about the topic from GMTK (What makes a good detective game).
Definalty a tough challenge :D