does anything exist as good debt?

Yes certainly. But again it depends on how to manage it. If you can't manage it well, it can turn to bad debt.
A mortgage is good debt as it helps to build an asset. However, you need to make the payments on time and be current on the loan. I would say credit card is also good debt as it helps to build credit reports and scores. But, you need to make the full payment within the billing cycle and not roll the debt.

I disagree with Mabelle Page regarding one point. Credit card debt can never be a good debt. It's a bad debt. Student loan is a good debt since it helps to build your career. But again, you should start making payments on the loan after graduating from college. But try to avoid borrowing a huge amount if possible.

Yes, obviously! Good debt is an investment that will likely grow in value or generate long-term income. I would say that opting for a student loan is a type of good debt. It can help you to earn a higher degree and increase your earning potential. Another example of good debt is a mortgage loan. Mortgage loans have usually lower interest rates and that too tax deductible.

Evry debts are good if you repay then within time.

I believe every debt which turns out to an asset after making the full payment is a good debt. Mortgage , car loan, is good debt.