Why it's hard to practice my Korean language skills

First of all, I'm in Korea mainly to teach English. And my host family decided to host me because I'm a native speaker. But it's more than that. I really wish Korean people wouldn't continuously tell me how good my Korean is. It's not very good. After anything more than a 30 second hello with any teacher at school, the conversation topic usually switches to how good my Korean is. If I was Korean American and didn't know any Korean when I arrived in America, the conversation would usually be about why my Korean sucks.

Yesterday was classic. It was the Korean memorial day, so there was no school. The halmoni (grandmother) cooked meals for me and my host siblings because the parents were out playing golf. Anytime I asked the halmoni something, or we said something, there would always be [oh, he speaks Korean very well] at the end. But then she would talk to my host sister about me like I couldn't understand.

Me: [halmoni, did you finish dinner?]
Halmoni: [yes]
Me: [was it good?]
Halmoni (to host sister): [he speaks Korean so well! How long has he been here?]
Me: [11 months]
Halmoni (to host sister): [he understood! he eats Korean food so well too. Ask him if the meal was delicious.]
My host sister Ji sawn: Was it delicious?
Me: Yes
My host sister Ji sawn (to halmoni): [he said it was delicious]
You just can't stop the halmonis in Korea.

And an example from running into one of my host mother's friends on the street:
Me: [hello!]
Her: [Ben, hello]
Me: [how have you been?]
Her: [oh you speak Korean too well!]
She hits me on the arm and then keeps walking.