"I do not know Spanish" in Spanish is "Yo no sé español(emphatic)", pronounced: ['ɟ͡ʝo. no. 'se:s.pa.'ɲol]. Actually if you're infering that you don't speak Spanish the correct response should be , "Yo no hablo español (emphatic) ['ɟ͡ʝo. no. 'a.βlo̯es.pa.ɲol]" which translates to I don't speak Spanish.
No, mi hablo espanol.
no sé decir eso
This is how u say it in spanish: que quieres saber?
Translation: Sabes español?
¿Sábes qué? = Do you know what?
¿Me conoces?
i didn't know that you speak spanish = no sabía que hablas español.
Yeah, I do...lol did you mean, How do you say, you know lots of Spanish? If that's the case, then you say,"Sabes mucho español".
Do you know about that is: Sabes de eso
No sé.
Ellos saben.
" Sabes que"
¿Sabías que?
No sé