Bot that parses the posts from the channels to the telegram in which I am a member and repost them in my channel. How?

The first thing may sound strange to go to Google, understand how it works, do a couple of three tutorialnya bots, as you will understand, come of the court

No way. :)
So says Google
The bot is in the channel, that he was in the channel ADMIN channel should be added to the channel with ADMIN rights

There is such a thing IFTTT read more about it, too, was looking for something like that.
Here are the links:
\rhttps://vk.com/page-64980878_50290680
\rhttps://habr.com/post/269819/
\rhttps://womenbz.ru/telegram_for_business

I would have tried to look in the direction of headless browsers (puppeteer) and the web version of telegram.
Topic: report of Yegor Malkevich — (-- Steal --) Extracted data from the Internet

It will be not a bot I mean Bot API telegram, and the bot in the classic sense of the word, that is, that emulates the user of the service. As the telegram open, you can take alternative clients, the type of telethon, for example, it is not so difficult to implement the functionality of reading the selected channels and posting any messages to your channels/chats