Again, 'I'm' is used here as 'I am.' 'Good at' informs someone what you excel at and are comfortable doing.
Here are some examples:
I'm good at drawing. I'm good at swimming. I'm good at driving. I'm good at writing. I'm good at math. ____________________________________ #English_conversation #Learn_english #English_grammar #speak_english _____________________________________ Practice English Everyday | I'm good at