I finished it! My bad for the deleted post, I messed up while trying to add a reply.
I didn't connect a lot of the pieces until the end of the game, but I still ended up missing only 2 entries! The locked picture had me messed up in the earlier game (lol), and I couldn't figure out the surname for the second locked person. I overlooked a lot of clues in hindsight or straight up forgot about them, but the notebook feature was incredibly useful, because I was able to write down key points I'd found out and not have to seek the sources out again (mostly).
If you're planning on playing this, I'd really recommend to do the same! If something seems even a bit important, write it down in your notebook. And even if you've already looked at something, it's very useful to go back multiple times. Pay attention to the intuition points!!
Anyways, I love this game. I'm going to replay it in a year or two, once I've lost all memory of the mystery. To whoever is reading this, have a great day! ^^