Confused on what backend framework to use to talk to an API.

My friend and I are wanting to write an Android app that will talk to our personal server that will talk to an external API. I am confused on what framework to use to talk to the API and then having our app access that info.

I use Spring at work, but from my understanding it is used to create you own API, not for talking to one. I like spring because of the annotation request mappings you can have, but that doesn't make sense in our case because we are talking to endpoints, not creating them?

So we have our personal server and then we make calls our to an API to get meaningful info about this certain product. We manipulate the data and talk to our database as well and have methods that do actions we want with that info. We then use our Android application to talk to our service on our server. So I guess my question is do we even need a framework to help us talk to the API easier or can I actually use spring or something else to help us talk to the API?