if you use informal language with your friend say : Ты можешь, пожалуйста, говорить помедленнее? If you use formal language: Не могли бы Вы говорить помедленнее, пожалуйста?

[пожалуйста] Не могли бы вы [] говорить немного помедленнее, [пожалуйста]? Is the form with "could you" etc. But it is really too long one:-/ [] - is the third place where 'please' may occur. It breaks the phrase apart and thus implies delibirate play with intonation... Говорите, пожалуйста, помедленнее. Говорите помедленнее, пожалуйста. Note that in this phrase putting 'please' in the beginning of an imperative-phrase can make your tone sound insisting. Any variations around : Это для меня слишком быстро. - it is too fast for me Все ёще слишком быстро - [it is] still too fast. [please] можно чуть помедленнее [please]? It is an informal wording. "is·it·posssible/allowed a bit slower". Family, or a collaboration betwen friends. Also in shops sometimes. Obviously you will need shorter phrases in some contexts. Не могли бы вы повторить... ? or Повторите, пожалуйста, немного помедленнее. Vocabulary: повторить - repeat. говорить - speak сказать - say. немного, and its less formal (but perfectly literary) synonims: чуть, and чуть-чуть. - a bit. Use them by taste before 'slower'. Медленнее vs медленней, Помедленнее vs помедленней ------ by taste. Absolutely. Depends only on the rhythm convenien for the speaker.

Thanks to everyone! I'm glad I asked!

Dan, prepositions stick to the next word. In some 'preposition + noun' groups the stress falls on preposition, as you will note - and the old Russian vowel ъ (it was a vowel once:))) which gave [zero] or [o] in the modern Russian dropped form many of them (въ->в/во). It would never happen otehrwise, because it's their only vowel:)

It is common not to stress function words, like prepositions, and when they are not stressed, they tend to unite in one whole. 'До' in 'до свидания' is almost always not stressed. This happens in the same way in English (think of 'a cup of tea').