Complex sentence: Gradually Inga and Maksim understand that only the perpetrator poses as a fighter for the truth at the heart of its action is the motive of personal revenge, while the main enemy is Maksim himself.
Split into simpler sentences: Gradually Inga and Maksim understand that the perpetrator is only posing as a fighter for the truth. At the heart of the action is the motive of personal revenge, while the main enemy is Maksim himself.