Which countries are available to do Safe Transaction? - All countries, there are no exceptions.
Which wallet is the real one for transferring NFT to it? - The only and real one is safetransactions.ton
How long i need to wait since i sent Safe Transaction? - If Seller/Buyer do not accept your Transaction, after 1 hour it will cancel and you will get TON back (0.05 TON fee will not back to your balance)
Which NFT's i can buy with Safe Transaction? - All of which were sold on GetGems.io.