Obv I don't know you from the man in the moon (oh wait -- him I DO know

)
anyway
Normal to be wazzing out a bit but NORMAL procedure is to have consultations w/your degree advisors
Dunno how the whole process goes where you're from but here it is indeed a process, getting a thesis/dissertation subject and outline sorted out & approved. My only instinctive reaction is to go w/YOUR instinctive reactions at first: What fascinates you, what facets of your subject matter rly get you going & make you wanna dig deeper? Make list and take it to your advisors'/tutors meeting(s)
& jot down notes while you're there (listen a lot)
Luck. Pursuing a big thing like a grad level dissertation is always a learning experience in & of itself, pretty exciting imo --- & can be either utter misery in the execution or rly rly amazing
Lots of work, and doing it properly is hugely validating.
But I'm a geek who loved it, so maybe you should NOT be asking anyone like me bc of said prejudice. heh
Chyia, remeniscent