Can't help but notice you have a lot of these type questions. How about trying a resource to help you with the right meaning and then you can try to use them rather than just asking for definitions. Anyway, this one means the thing is much deeper than what is already known or already done. Such as, "We've only scratched the surface of learning English." or "After working on this project for 3 days we've only scratched the surface."

Juse be yourself and do not feel too much pressure on that. You will learn English very well.