Question

What happens when the hydrogen of our sun completely turns into helium? (hint: I know the answer)

Answer 1

Then the sun would not exist only

Answer 2

The Sun will become a Red Giant.

Once the core hydrogen is exhausted in 5.4 billion years, the Sun will expand into a subgiant phase and slowly double in size over about half a billion years. It will then expand more rapidly over about half a billion years until it is over two hundred times larger than today and a couple of thousand times more luminous. This then starts the red-giant-branch (RGB) phase where the Sun will spend around a billion years and lose around a third of its mass.