Let me try! :) 1. I don't understand. わかりません。 2. I don't know.　しりません。　(in many cases you can still use わかりません though) 3. Can you repeat that please. もう　いちど　おねがいします。 4. Can you speak more slowly please. もう　すこし　ゆっくり　はなして　ください。 5. You speak too fast.　はなしかた　は　ちょっと　はやすぎます。。。 6. Can you speak more loudly please.　もっと　おおきな　こえ　で　はなして　ください。 7. Can you spell that please. - not sure of this one. Perhaps you can try かきかた　は　なんですか。 8. What is this?　これ　は　なんですか。 9. How do I say ____ in Japanese?　______は　にほんごで　なんと　いいますか。 10. What does ____ mean in English?　______は　えいごで　どういう　いみ　ですか。

Fer has already answered you and I'd like to add more: 5. You can also say: あなた の はなしかた は ちょっと はやすぎます。or simply ちょっと はやすぎ ます。because we often omit some things when we already know what we are talking about. 7. かいて もらえます か。(the literal translation is "Could you write (it)?") どう かきます か。("How do you write (it)?") I hope this was helpful.

Ferさん and Ryokoさん have already answered completely. But I dare introduce this article to you on italki. It might be helpful for you. http://www.italki.com/article/300/important-phrases-and-vocabulary-for-your-first-japanese-lesson#.VOAyBC5RrTA