Except for the word "like" it is grammatical. But it is not elegant.
Thank goodness I know how to swim. It would've been so much harder for me, you know? Like, I'm talking about when I was learning how to surf.
Can this be said during conversation? Is it grammatical?
"Thank goodness I already knew how to swim when I was learning how to surf. Otherwise it would have been much harder for me, [you know?]"
Your sentences are OK. Plenty of people speak much worse than that. But strictly it's illogical - saying "you know" when you still haven't given enough information for the person to know anything. Also, "Like" is not needed; it's best not to pick up bad habits while you're learning.