Yeah of course! I’m more than happy to answer any questions about it. For starters, not all the songs are LawLu per se. Quite a few are actually examinations of his own psyche or relationship with himself, while others are relationships with say Corazon (Saturn for instance) or Doflamingo (Dark Matter and Torture).
Believer I associate more with himself and overcoming his trials of youth. The rebellion to break the cogs of the world and disrupt the passing status quo. It’s a bit directed towards Doflamingo as well since he feels made by Doflamingo, taught him about pain and revenge. I also associate the song heavily with One Piece because of two AMVs. I’m on mobile right now so I can’t link them now, but I can later.
Thanks so much for the ask! Hopes it answers your question satisfactorily. If anyone has any more questions feel free to send them!