scratch the surface["수박 겉핥기 식으로 알다"]

scratch the surface

: to learn only a little about something

  "수박 겉핥기 식으로 알다"

 1. I have been studying English for two years,

    but I've only scratched the surface of the language.

    There are many important rules and vocabulary that I still don't know.

 2. I visited India last year. I really didn't get to see much of the country;

    I only scratched the surface.

    I would like to visit there again and see a lot more.

 [주] get to ; = get a chance to