Believe Your Supervior
Doing PhD is a tough work! I have already heard many PhDers around sighing with that feeling, although this is just the beginning of my PhD life.
Everything of doing research is difficult, at least I had enough feelings during my Master. To learn new knowledge is always hard, expecially when you need it in the next week. But now you even do not know the conception of it.
If you do not hate it now, I believe you will be interested in it in the future.
Our superviors usually have strong background in a research field. They probably has been observing some specific disciplines more than decades. Hot topics are in their mind. Valuable research directions is total clear, but they just don’t have too many brains to clear every detail, and they don’t have enough hands to write it down.