My project was mostly independent, so I was responsible for managing my time and planning what to work on, but in the office I was surrounded by other project managers who could answer questions and help me out. I learned a lot just from watching the nonprofit running. My supervisor was busy, but nearby so super accessible and encouraging.
What I wish was different
I wanted more field work (in the case of my project, planting butterfly gardens) and less time at a desk.
Always ask questions. Wherever you are, there is so much to learn from the people around you, and they will be so happy to help you or tell you stories. Even if a question sounds silly, they will be glad that you care about doing your best work.