1. I'm seeing the manager tomorrow morning. - correct
2. I'm feeling hungry. Is there anything to eat? - correct
3. Are you believing in God? no I’m an atheist. - wrong: Do you believe in God?
4. This sauce is great. It's tasting really good. - wrong: It tastes really good.
5. I'm thinking this is your key. Am I right? - wrong: I think this is your key.