Why does GDP omit the sale of used goods, of financial transactions, and government transfer payments?

Hello, can anyone please help me answering questions on Macroeconomics ..

1.Buyers always prefer lower prices to higher prices. Do you agree or disagree? Explain

2. If the unemployment rate is 4%, does if follow that the employment rate is 96%. Explain

3. I just heard on the news that GDP is higher this year than last year.This means that we are better off this year than last? Explain

4. Why does GDP omit the sale of used goods, of financial transactions, and government transfer payments?