Is it just me who's getting a little lost with how this is going?

No, me too… I can't understand shit.

Part I- Kang is spending time with Taeyang

Part II- Kang informs his family that he’ll be changing specialities (his grandpa always wanted Kang to do a specific career as per his grandpa) as a doctor because of Taeyang. His grandfather does not say anything anymore about that and informs Kang that he went to visit Taeyang which makes Kang mad. Grandpa also tells him to watch out for what he cares about since others are also after the same thing.

Part II- Kang goes to his office and finally finds out through an investigation that he was all wrong about Jooseon and blames it on the blondie.

Hope that helps.

Thank you very much, I needed it