How to connect Android application with website?

Can you suggest any site or article where it's written in detail how to connect Android app with the website? How to work with the API to send requests to the server and receive responses from the server?
The site is organized so that there are a lot of galleries with pictures. How to organize application work with them(view, zoom, etc.)?
July 4th 19 at 23:42
2 answers
July 4th 19 at 23:44
1) the site should be an api which gives the information
2) pictures need to be in different sizes, otherwise it will lag (this is very important for listalki first give small priluchki, then if you need to load full size)
3) for queries recommend retrofit
4) for asynchronous podgruzki pictures picasso
July 4th 19 at 23:46
For starters, you can read a couple of my articles.

Here is an example API:

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