は苦手なんだ

I'm not good with ...

→ は
phrase Rare #30,216
I'm not good with ... Used after a topic to say that the speaker is bad at, uncomfortable with, or does not like something. なんだ adds an explanatory or emphatic tone and is casual.
JA: 私は人前で話すのは苦手なんだ。
EN: I'm not good at speaking in front of people.

チョコレートは苦手なんだ

I’m not a fan of chocolate.

キノコは苦手なんだ

I’m not a fan of mushrooms.

この手のことは苦手なんだ

I'm not good at this kind of thing.

は苦手なんだ

I'm not good with dogs.

子供は苦手なんだ

I'm not good with kids.

地理は苦手なんだ

I'm not good at geography.