Hi PEO, I was just wondering why the prime minister can't be the representative of the English King/Queen in Australia (Governor-General)?
The King and Governor-General

Parliamentary Education Office (peo.gov.au)
Description
His Majesty King Charles III, Australia's head of state.
Shown beside him is the Governor-General, Her Excellency the Honourable Ms Sam Mostyn AC, the King’s representative in Australia.
Thanks for your question, Ben. The short answer is that if the prime minister held both roles it could give one person too much power.
Australia is a constitutional monarchy which means the British monarch – king or queen – is our head of state. In Australia, the monarch is represented by the Governor-General. Their role, which is outlined in the Australian Constitution, is to make sure the Parliament follows the rules in the Constitution when it makes laws.
The prime minister is the leader of the government, and the government introduce most bills – ideas for laws – in the Parliament. It wouldn’t be fair if the prime minister also decided if the rules in the Constitution had been followed, because that would mean checking their own work.
Unlike the prime minister, the Governor-General does not sit in the Parliament, make speeches or vote on proposed laws.