Example of i'm good

A: Wanna grab a dinner together ? 

B: I'm good. Thank you. 

A: Would you like a cup of coffee ?

B: I'm good. Thanks though.

A: Can i give you a glass of water ?

B: I'm good.

A: Would you like to join us ?

B: I'm good. Thanks.

A: Just let me know if you need any help.

B: I'm good.