"Your words are good."
Translation:As suas palavras são boas.
It depends on context. I believe that just in a few contexts estão would be used. Like, if the person says that what one talks is usually something good, then são is more appropriate. But if you are, for example, reading/correcting a child's text, you could say "As suas palavras estão boas" if you want him/her to know that you like his/her choice of words. Something like that. :b
possessives 95% of times will come before the noun they are possessing. You CAN invert the order if you know what you're doing (like in literature, poetry, or if your sentence structure is trying to emphasize something in particular). The word order is not set in stone in portuguese, but there is a usual "direct" order that is easier to understand and should be preferred.
Well, although it seems odd to an English speaker, saying things like "o seu" and "as suas" is a feature of Portuguese. At least in Brazilian Portuguese this style is optional and in most cases you can simply say "seu" and "suas" instead. The cases where the article must be used or must be omitted are mentioned in this discussion: https://www.duolingo.com/comment/64947