American Slang Post
I’ve noticed that this phrase we use tends

to confuse people learning English. In America, we use the phrase “tell me about it”. However, when we use this phrase, we aren’t asking you to tell us about anything. We actually are agreeing with you you are saying, or saying that we understand it as well. We are being sarcastic, because we have experienced what you are talking about, so we say “tell me about it” ironically, as we have already experienced it. Though this phrase is sarcastic it’s not rude. However, I would reserve it for a more casual conversation
Example Sentences:

“This computer doesn’t work!” “Tell me about it, I’ve tried to to use it so many times.”

“I had such a bad day.” “Yeah, tell me about it. My car broke down on my way to work today.”

“”I hate the rain.” “Tell me about it, I haven’t dried off yet!!”

Hope that this helped and feel free to ask any questions in the comments :)