What is the ideal database to use for an application that will hold unique user data of an expandable list of dictionaries? [closed]

I created a fitness tracker web app, currently I am using mongodb as the database. In my app each day will be a new dictionary of various keys that I will then push to a list in the User Schema. I wanted to use Mongodb but each document will can only have a maximum size of 16 megabytes, so it will get filled very quickly. I want it hold as much data as possible to be able to log the information as a chart so the user will be able to see their progression over time. I have only used mongodb but I’m willing to learn any. What would be the ideal database to hold such data.