But I still don't know how to detect scams fraud etc
Sometimes it is easy other times not. It is best to avoid sending money to anyone without understanding what is happening and how scammers may trick you. Generally if you want to invest you will have to trust an exchange and pass KYC in some of them. Bitcoin is P2P though, meaning you can buy from someone directly. You may try this forum too as there are some trusted members that can be an escrow for the deal and make it without any problem.
To detect scams in general first of all you need evidence. For example in the case of new projects a plagiarized whitepaper, fake team members, etc. There are other red flags but you will need concrete evidence that they are scam. Sometimes these are hard to find but they are always there the entire time.
A good way to understand scams and how people detect them is looking at this thread: Scam Accusations