Well, since "coffee" isn't an innately japanese word, it's to be written in katakana. Also the "一" is used for extending vowels. Without it, it'd sound like "kofi", when it's more like "koofii".

Should kohi be in katakana? I never know when to use which, also, what does "ー" mean?
And no i didn't miss the だくてん on purpouse, thanks for pointing it out! 

I'm not sure if it was on purpose but you forgot all the "だくてん" from "ありがとうございます"