Every language has interesting words, but non-native speakers of that language can't learn these phrases 100%. But only if you don't learn British English, because I can help you with that. Here https://www.anglotopia.net/site-news/featured/british-english-the-top-50-most-beautiful-british-insults/ you can learn the top phrases that will help you in Britain. They're not cultural expressions, but they can help you understand more about British culture