Relating Collection Types and Data Structure

well so far i only make an api call to /api/balls
i tried some stuff with populating the fields and stuff but if i go via /api/soccerteam/?populatetherelationfield it returns everything from the soccerteam but if i go down to the relations there are some fields missing which i was expecting to get returned like for example the media field that shows the specific ball. i expected that to be part of the objects in the array of relations.
im not even sure if the approach is correct.
or to explain it on other terms:
every strapi user is part of a team and i want to display stuff to the user depending on the team he is part of. if i could build everyhing from the ground up i would just use components and repeatable fields i guess cuz that is very similar to how it works in wordpress. the issue now is that i have to adjust a running project and i need to redo a bunch of collection types so they can be displayed depending on the team of the logged in user.
so i somehow have to map existing collection types to the team. another thing is that i need to be able to change specific fields of the ball collection type “globally” so lets say i want to update a link thats part of the collection type ball - that should be updated for this type of ball no matter to which of the teams it relates - so i guess it HAS to be a seperate collection type instead of being a component within the team. forgive my babbling i hope u can roughly understand what i am trying to do here. im very new to strapi and lack the proper vocabulary…