Don’t be confused any more, Idioms and English Expressions are easy to learn and will make you a better English speaker. Native English people know these expressions by heart, and so can you.
Idiomatic expressions are the difference between an intermediate speaker and an advance or proficiency speaker, take the next step and speak English like a native.
Why learn English with non English native teachers, it doesn't make sense, the only way to speak English as a native speaker is being taught by a native speaker.