Salam, "الفـطور" means breakfast, while "الإفطــار" means the process of eating breakfast. So, I think the correct way to translate "I think it's breakfast" is "أعتقد أنه الفطور ". It would be better if you could provide more context.

Both are correct, you can use both الإفطار or الفطور to mean breakfast. But you can't use الإفطار to mean lunch or dinner, it's only used when talking about breakfast or Muslim's first meal after fasting in Ramadan.