Hi, I'm also in my first year, new to the forum and feel the same! I have three children and work at the weekends, so constantly feel I am behind or peddling hard just to keep in the game! My supervisors seem happy with my progress at the moment, so I guess it is mostly imposter syndrome. But its hard to feel reassured as everyone in the department seems to be working at such a pace and I'm just plodding along, finalising my research questions after 5 months of study!!!! 

I just try to keep at it and hope I can prove myself as worthy - I'm learning loads along the way though :-)

Good luck - I try to prioritise the essential tasks and get on with those first.