There are many renditions of the text that include side-by-side modern day language in order to help you better understand Shakespeare's language. Although his words seem complicated when compared to the current English language, it is important to remember that part of the beauty of his plays is the way in which he is able to manipulate words and create lyrical strings of text that are song-like in nature and, when read aloud, can be quite inspiring. For these reasons I suggest you find a side-by-side text and read both Shakespeare's writing and the modern day writing so that you do not lose the original text.
We also have an etext here on eNotes that has footnotes to help you easily understand what Shakespeare is trying to convey. The link for that is here.
Here are some links to different renditions of Romeo and Juliet with translated text:
This one has the original text on one page and a modern translation on the other.
This one has the original text on one page and explanatory notes on the other.
Remember that if you are having trouble understanding Romeo and Juliet you are not alone! We have an abundance of resources here on eNotes under the Romeo and Juliet page to help you better understand this play.