"Honestly, I don't know how to speak or write English."
Let's break it down:
* La neta: This is a slang term for "Honestly" or "Truthfully."
* el inglés: This means "English."
* no lo sé: This means "I don't know it."
* hablar: This means "to speak."
* escribir: This means "to write."
The sentence is grammatically correct and expresses the speaker's lack of English proficiency.