What to use to create contacts on Android?

Question

Android

I am not a professional Android developer, but from time to time I make various applications for myself and my needs.
Task:
There is a customer base (about 5000) people. From time to time one of them calls me on my mobile. I would like to immediately know who is calling, what city he is from, and if possible, additional information: the last order, the address of the nearest office, etc.
Entering everyone manually is unrealistic, I have already tried it. I forgot, then I scored, then something else. Someone changed, then moved.
Implementation:
I would like to make an application that pulls up a database of clients from my web service. And with an incoming call, it displays the necessary information about it.
Question:
All sorts of skypes, vatsaps, etc. penetrate into "native" contacts and add people there. I would like to implement something similar: all clients will always be in the notebook, while manually entering them will not have to.
In what way is this done? What to google, as they say? :)
I can quite understand the technology, but I don’t understand what exactly to look for and what this technology of embedding in contacts is called.

Answer 1

https://developer.android.com/training/contacts-pr...
This is for contacts. For call interception, google android call receiver

Answer 2

you can, for example, google "custom account type" and "syncadapter"