"Been there, done that!" is an everyday English expression used to convey the fact you have already done something. It generally conveys the meaning that you already have knowledge or experience of something.
"Been there, done that!" can refer to having done a similar activity before, visited a place earlier, or got information much before anybody else.
1. When Amit excitedly told his friends that he had trekked down to the base of Jog Falls Karnataka, his friends laughed and said in unison "Been there, done that! We went last weekend."
2. The new engineer behaved as though he knew all about the project site and the machinery being used there when actually two other engineers had been there, done that.
3. Before Sharmila could ask her friend if she had reported to the police about the theft in her home, her friend said "I know what you are going to ask – been there, done that!"