Java - How to get all messages from telegram channel where I'm not Administrator?

I need to get all messages (or latest 30-40-50) from a Telegram Channel where I'm not Administrator. I've tried to integrate in my Java application some solutions founded on github such as https://github.com/rubenlagus/Deepthought but the documentation is very POOR and I'm in trouble. So I ask some help... Has someone successfully solved this type of problem?