Telegram is a joke. They roll their own encryption, screwed it up massively on Day 1 in exactly the ways that everyone who says "don't roll your own encryption" predicted they would [0], and make snake-oil claims about their security while responding to legitimate technical criticism with conspiracy theories about how their intelocutors are all agents of the U.S. government.

[0]: https://news.ycombinator.com/item?id=6948742