To sound like a textbook means not sounding natural and relax when you speak. The way native speakers speak is not necessarily the way language is taught in a textbook, as there are other variables at play that occur as you communicate with someone. (Pronunciation, Rhythm, intonation, filled words (words that fill pauses in conversation, e.g. “hmm”, “you know”), linking of words, etc. To become a more fluent natural speaker (even with an accent), learn about the sounds of the language, notice the problem areas, and practice speaking and listening. As per your second question, “literate speech” sounds like a textbook to me! (Unless you need that formality in your speech)