～が下手【～がへた】

へた下手 means "bad at". The thing you are bad at takes が and the person takes は. A verb needs の in front of が, which turns it into a noun.

• × 話すが下手です → 話すのが下手です

こと can stand where の does, but it sounds stiffer: うんてん運転することがへた下手です.

下手 or 苦手

下手 is about skill: the result is poor, whoever judges it. にがて苦手 is about you: you are weak at it, or would rather avoid it. Something that is not a skill – getting up early, a food, a kind of person – only takes 苦手.

• × 早く起きるのが下手です → 早く起きるのが苦手です

Yourself and others

Calling your own skill 下手 is ordinary modesty, and it is the usual reply when someone praises you. Said about someone else, 下手 is blunt; あまりじょうず上手じゃないis gentler.

Before a noun, 下手 is a な-adjective and takes な.