Hahaha are you serious?? Its אלוקים with ה youre not supposed to say not God. Doulingo sure makes me laugh sometimes.
G d or G-d is a common way of writing it when you're not actively/intentionally meaning the name, as when you're practicing a prayer but not actually praying. It's an orthodox practice that not all liberal and secular Jews share.
This is a disputed issue. Some argue that this practice should be applied to the names of God in all languages used by Jewish peoples, while others believe it should apply only to the sacred Hebrew names.