How to use Telegram Rest API?

Question

Java

Maybe someone has simple examples of using Rest Api Telegram, preferably in java. For example, to check the phone auth.checkPhone, I send these requests to the documentation, but it still does not work. There are a lot of tutorials on the Internet about bots, where they explain everything right on the fingers, but there is practically nothing .. for the rest api.
(And by the way, why are questions on this topic on stackoverflow often ignored or downvoted?)

Answer 1

divide "does not work" into parts and start from the nearest