Added extra levels for some adventures (hedyorg#594)

* Added extra levels for some adventures

I've added lvl 6,7 and 8 for the restaurant, lvl 7 for the story, lvl 8 for the song and lvl 7 for the calculator

* quotation marks added for ask commands

quotation marks are now added to every ask command in the example codes.

* fix filename for dutch adventures

* small indentation fix in calculator

Co-authored-by: Felienne <[email protected]>