Urban Dictionary, in your language
You shouldn't need to understand English slang to read the explanation of English slang.
With Ask Urban Dictionary, you can ask about a word in your own language and get an explanation in that language. It draws on definitions written by Urban Dictionary contributors, so those entries become accessible to people who couldn't comfortably read them before.
And you can keep talking. Ask what makes an expression rude, whether it can be affectionate, or what changes when it's used in a different sentence. Ask for another example if the first explanation doesn't click.
This is especially useful for words that don't have a neat equivalent in your language. A one-word translation can leave out the joke, the tone, or the reason someone chose that expression. A conversation gives you room to ask about those parts.
Start in the language you're most comfortable with. You don't need to switch to English to get closer to what someone means.