Although the GraphQL Schema Language is not that hard and the Graphiql tooling integration helps a lot, I still sometimes have to fall back to the documentation to know how to do something.
To help you even further, you can start using the GraphQL Schema Language Cheat sheet(more information here: https://wehavefaces.net/graphql-shorthand-notation-cheatsheet-17cd715861b6). This gives you a one pager in PDF or PNG with the full syntax.