Do you know any tips to become a polyglot?

Use apps to learn a language, speak it conversationally, take online classes once you are near conversational for it to improve more.

Regular and serious practical application and study is the key. Learning how to learn a language is the most difficult part, but once you understand how to break down a language to its components, and can relate those to your own interests and learning style, it will become easier to learn new languages. However, language fluency can fade over time, so it is important to keep maintaining your language use over time. The internet is a great tool for this, since you can talk to people from all over the world and watch videos in almost every language that exists!