じょうず(上手) and へた(下手) are both なadjectives and they are used to describe people’s strong points and weak points.
[person] は [activity] が じょうず です。= [person] is good at [activity].
おっとは りょうりが じょうずです。
My husband is good at cooking.むすこは サッカーが じょうずです。
My son is good at soccer.
ちちは えを かくのが じょうずです。
My father is good at drawing pictures.わたしは いねむりするのが じょうずです。 – Japanese people don’t usually use じょうず for oneself unless making a joke like this.
I’m good at drifting off.むすめは ピアノを ひくのが じょうずじゃないです。
My daughter is not good at playing the piano.
[person] は [activity] が へた です。= [person] is not good at [activity].
わたしは そうじが へたです。
I’m not good at cleaning.ははは おせじが へたです。
My mum is not good at flattering people.おっとは うそを つくのが へたです。
My husband is not good at telling a lie.
If you add に after じょうず/へた, that can become an adverb and you can commend others.
じょうずに かけたね。
You have drawn (a picture) well.とても じょうずに ピアノが ひけました。
(a person) played the piano very well.