They can contest to the bank that they've used to send you the payment and have it refund without you knowing it.

Rates vary from time to time because of bitcoin's volatility. It can stay as much as it can for just the same price but you have to expect that it won't stay for just one price. I agree with OmegaStarScream that even though you had multiple trades with that guy, you still have to be careful and always be cautious and alert when you deal.

I don't think that the changing rates are something you should be cautious about because as far as I know, the value gets locked once you initiate a trade.

As for tips:

- If the bank transfers are local and assuming that trading cryptocurrencies are not an illegal thing in your country, it might be a good idea to ask the user for his ID. This can help you with law enforcement in case things ever go wrong in the future.

- Just because you're trading with the same person, doesn't necessarily mean he is trustworthy. It's all about the amount you're exchanging with him. In other words, don't trade 100$'s and then suddenly ask for a 5000$ deal and assume that things will go just fine.

- Proof of the bank transfer. Not sure if you're expecting him to deliver a receipt, or a screenshot, or whatever when he send you the funds but this can help you open a dispute later in case you get scammed. Paxful may not get your funds back, but at least, he'll get banned.

Some of the tips above depend on the amount. You shouldn't expect people to provide their IDs and personal details for small deals.

Yes. They can always withdraw the bitcoins you sent them and then chargeback the transaction with the bank.

If I were you though, I wouldn't be too paranoid. Just make sure to select someone with a good trust score, and who has been on the platform for quite some time.

Paxful is not a central/bank/exchange site to buy cryptocurrencies. It is a site that provides a trusted escrow for people who want to buy and sell bitcoins.

Demand and supply are what make the price different from the average price that show on CMC or any other site.

Since you are a beginner, stay away from the deals that give you the highest price. Rather, look for reliable people. It is true that they give less money, but with time  you can improve your chance of getting better deal.

Remember to read the terms of use of the site, Paxful is full of scammers and the available escrow requires people to have basic information about Bitcoin & Paxful TOS