@wojciechpaluch I’m not that familiar with Contact Form 7’s codebase, but I imagine it should be possible.
WPGraphQL has many APIs for registering GraphQL Types and Fields to the Schema (https://www.wpgraphql.com/developer-reference/)
Depending on the project, you could manually register specific queries/mutations to the Schema that match your forms.
If you want it to be more programmatic, where any form created in CF7 automatically shows in the GraphQL Schema, that would be a heavier lift, but probably possible.
Depending on how Contact Form 7 is built, you might be able to get a list of the forms and the form fields and map those to WPGraphQL as queries and mutations in the Schema. Then anytime a new form is created in CF7 it would automatically show in the Schema.