I want to share my own experience because ı think it works

1. find a language that close to your native one ( even if that is not your favorite one )
2. learn the alphabet of the new language very well
3. and start to learn
4. go on

for example, if your native language is Persian and speak Turkish fluently you can learn Azerbaijani easily, and Azerbaijani helps you to learn another language because languages are linked together in different ways as I see.

Note: this is a way that I find for myself and learn a new language 🙂 I’m not an expert