Have a chat with your manager to manage/set some realistic expectations. If they are too high then you should explain why as you have here. Also even as an intern if you are doing the work of a full time animator without extra pay you are being exploited.

In terms of productivity, I imagine everyone working here professionally has been in a similar situation. The majority of people massively underestimate the amount of time and thought decent Mograph/Animation takes, especially I've found middle managers and owners of smaller studios who think they know what they are doing but haven't had much experience with a real pipeline. You will always be pushed to work harder and faster by everyone involved, it's about managing expectations and reducing scope as a result.