Because I’m getting such a late jump on this, we’ll keep it simple: yes and no.
“No” is لا (lā) and can be used both as the reply to a yes-or-no question and to negate a present-tense (but only present tense!) verb: يَفْعَلُ (yafʿalu, “he does/is doing”) is negated as لا يَفْعَلُ (lā yafʿalu, “he doesn’t/isn’t doing”). Negating past and future tenses is more complicated and we’ll deal with that later. You may also encounter كلا (kalā) as an emphatic/interjection, like “No! Never!”
“Yes” actually gives us our first chance to see a divergence between spoken vs. written Arabic. In written Arabic you will most often encounter نَعَم (naʿam), and you will also encounter it in speech. More often encountered in speech, however, is أيوة (aywah), yet this is rarely encountered in writing.