For more advanced learners, here's an interesting article about where Lukas Graham grew up, Christiania in the middle of Copenhagen, Denmark.
Once I was 7 years old...we use this expression once very often to start a story (I expect you all know once upon a time...) Can you think of a story about yourself that begins Once I was 7 years old?
Here's a little story from my life: Once I was 7 years old, and I decided to put my coat on back-to-front and put the hood up over my eyes. This was really fun, until I walked down to the end of the garden and walked straight into a brick wall. (Yes, I did know the wall was there.) I got two black eyes.