database setup

Hi, I am a completely beginner in databases and backend. I am developing a flutter mobile app. This is my scenario, each user is a gym owner. Each gym owner has a list of lessons. For each lesson there will be the teacher, which is required and then the list of alumns that can be form 1 to 29. Teacher and alumns then have some attributes that are different.

I don't want to store teacher or alumns infos, for internal reasons every time the gym owner will have to manually write the attributes of the teacher and the alumns for every lesson.

At the moment each gym owner has only one gym but in the future i would like to provide multiple gyms for a single user.

What is the best way to structure my database ? I think i have to use relationships. In my scenario every time i will use teacher and alumns info in a couple of cloud functions and then i will mark the lesson as completed and erase all the lesson info except a few parameters for privacy reasons.