Whenever you have to paraphrase certain parts of Shakespeare plays, it is a really good idea to make sure you use an edition of the play which provides a key to some of the more antiquated expressions or uses of words that are difficult for the modern audience to understand. For example, in this speech of Balthasar's, he says that he "presently took post to tell" Romeo about what happened with Romeo, which refers to taking a post horse, that was a horse kept at an inn and rented out to travellers. A good edition of this play will help explain such anachronisms. Here is my translation of the lines you have indicated:
She is well, so nothing can be wrong.
She sleeps in the mounment
But her spirit is now in heaven.
I saw her placed in the tomb of her family
And presently tried to go to tell you of it.
Forgive me for bringing you this bad news,
As you told me to do this for you.
Hope this helps!