What would happen if you added more than 5 mL of yeast solution to the H2O2?

Answer: -

Hydrogen peroxide breaks down into water and oxygen.

2H₂O₂ → 2H₂O + O₂

The yeast present contains an enzyme called catalase which catalyses the reaction.

More the amount of the catalyst added, faster will be the decomposition of the hydrogen peroxide.

Thus if we added more than 5 mL of yeast solution to the 2H₂O₂, the breakdown would occur faster. Thus the bubbles and the accompanying fizz would be much more.