Hi few questions
1. why/why isn't parliament the supreme law making body?
2. governor VS governor-general (their roles, royal assent)?
3. separation of powers. Why are legislative and executive linked and judiciary separate from them?
4. why aren't laws made my the courts? Advantages and limitations courts making law.
5. why do laws need to change?
6. what are the strengths and weaknesses of parliament as a law making body?
1. Parliament is the supreme law making body as it has the power to make, amend or cancel laws in areas within its powers as it wishes and is not bound by any previous parliament's laws (concept of parliamentary sovereignty). No court may cancel the laws of parliaments unless they are made outside of parliament's powers (unconstitutional).
2. Governor is in the state's executive. GG is the in the federal executive. Governor-generals can withhold royal assent (stopping a bill from becoming law) in certain circumstances whereas Governors cannot withhold royal assent anymore. From then on both retain similar roles in ensuring parliament and government operates in their respective levels.
3. I have explained this recently. If you look up in this thread you would see my response to a separation of powers question a page or two up.
4. Courts are bound by parliament, unless parliament's law is unconstitutional and even then courts can only abrogate the part of the law which violates the constitution, and uphold the rest. Courts are not democratically elected and their primary role is too interpret and apply the law made by parliament, not make the law itself. Courts have made some laws, that is the common law, made by courts, however courts do not possess the same research tools and democratic responsiveness as parliament and thus courts are usually unwilling to make 'common law' today, or even change previous common law. Today most laws are changed and made using acts of parliament. (there is more to be said on this topic but I can't explain it all here in one post)..
5. Technological changes, protection of the community, change in community values, law becomes unacceptable in light of changing times/circumstances and many more reasons. It's all listed in the text with good examples.
6. This is a very broad question, I suggest you read the textbook and come back if you have any more specific questions on the content. We can't just give it all to you on here because there are so many things to say.
Many of the questions you asked have also been answered before so if you use the search feature you could find a lot more responses/information on these questions.