I’m going to believe you’re serious and also quite naive. London is one of the greatest cities in the world. Most museums are free, so natural history, science, Victoria and Albert for a start. The both the Tate galleries, the national gallery and the national portrait gallery. Every one of these is free.
Then there are theatres showing everything from musicals to serious drama, a bit of opera and ballet too in various theatres.
Then there are the sights, Buckingham palace, the Mall, Houses of Parliament. Beautiful paths like Hyde park and arcades park
Perhaps you want to eat every food imaginable from anywhere in the world
Then visit a few markets, Spitalfields, Borough, Camden, Greenwich.
And at that point you haven’t touched a shop - not Harrods or selfridges or Covent Garden
i can’t imagine why people come to London. There’s nothing at all to do