Ok I’m a lil confuse on why garam felt betrayed that the old guy invited the 5 other peo...

I’m guessing it was just the straw that broke the camels back. For a few chapters now garam been trying to make his shows about his own sound. The pieces he’d play and in what order, the stages he’d play on, the type of piano and the way he’d play and the meaning they’d have—to make his own sound, and every single time the prof would chime in or change his mind. I think he’s hurting because all of these accomplishments has been from the profs help and he thought for once he brought that crowd in himself, not from prof’s connections

they were having coversations about the professor letting loose on his grip on Garam and his career so Garam can make is own choices and can grow into his own artist and be successful without the help of his professor all the time. meanwhile the professor is not loosening his grip at all and keeps on arranging stuff for Garam. he‘s doing it out of love and because he wants Garam to succeed but at the same time it seems like he doesn't have the trust in Garam to be able to handle his career by himself.
so although the prof meant well, he was not honest with Garam and broke his promises

Because lately, prof has granted him more "freedom" and even went as far as to tell him to take care of everything to learn responsibility. Turns out he didn't really mean any of that, and Garam feels like he's been pushed around for nothing and that he has yet to prove his own worth without prof's help, who keeps interfering.