How to use these words: 좋은데, 먹고싶다/먹고싶어
Also, what's the difference between 먹고싶다 and 먹고싶어? I know both means "I want to eat" and 싶다 is the plain form of 싶어. Does one of them actually have different meaning when it's used in a conversation? Or maybe one is the conversational form and the other is written form?

Thank you in advance, hope someone can shed some light ^^

Question

How to use these words: 좋은데, 먹고싶다/먹고싶어
Also, what's the difference between 먹고싶다 and 먹고싶어? I know both means "I want to eat" and 싶다 is the plain form of 싶어. Does one of them actually have different meaning when it's used in a conversation? Or maybe one is the conversational form and the other is written form?

Thank you in advance, hope someone can shed some light ^^

Answer

Actually, "~먹고싶다 means "I want to eat~".
Yeah, "~먹고싶어." means "I want to eat~".
But "~먹고싶어?" means "Do you want to eat~?" 
Because there is '?' in sentence. It's interrogative sentence.

For example, "사과 먹고싶다" and "사과 먹고싶어" both means "I want to eat  an apple"
And "사과 먹고싶어?" means "Do you want to eat an apple?"

"좋은데" means "I like it!"