I'm (literally) lost and playing in the wrong order

Hello- this is my first souls-like game and it's great so far. The only problem is I think I've been progressing on some alternate route and I can't find my way to the proper one. I can't find Genichiro or get to the top of the castle no matter how hard I try.

When I started the game last week, I thought it was fairly linear- I beat the chained ogre, fought the other samurai mini-bosses, then the Shinobi hunter, and did all the Hirata Estate memories before fighting Lady Butterfly.

I never came across this giant snake, or headless, or blazing bull, or guy on a giant horse. Seriously, was I supposed to fight all this shit BEFORE taking out Lady Butterfly? 💀

I managed to fight those bad guys too but areas of the castle keep getting blocked off, so now I'm in some forest with monks. I beat the centipede and armored knight, but I just have no idea where to go. The cave doesn't seem to go anywhere. I want to fight Genichiro but the hardest part of this game so far hasn't been bosses- it's been finding out where I'm supposed to go.

Pls help. Even when I try to google it the information is too confusing for me and tells me to go back to NPC's I've never met or idols I've never found. Thank you.