N5
のがじょうず
To be good at, Proficient
トムはサッカーをするのが上手です。
Tom is good at playing soccer.
Explanation
「〜のが上手だ」 means you are good at doing something: 「日本語を話すのが上手ですね」 (You speak Japanese well). Form: dictionary form + の + が + 上手. It is mainly used to praise someone else, or to describe a third person's skill.
Mixed up with
Do not use it to praise yourself: 「私は〜のが上手です」 sounds arrogant. The modest way to say you are good at something is 「〜が得意です」.
When someone praises you with 「日本語が上手ですね」, do not answer proudly 「はい、上手です」; the fitting reply is 「いいえ、まだまだです」 (No, I still have a long way to go).
Do not tell an elder or boss 「上手ですね」; it sounds like you are grading them. Say 「素晴らしいです」 instead.