I am guessing that you are asking how it would sound if it were grammatically correct in current day prose form. Poetic form is different of course. In Shakespeare’s day, poetry was mostly structured in popular rhythm and meter forms like iambic pentameter and word order was mixed to stress certain words or juxtapose images. These days, poetry is much less restrained by form.
But in terms of translating this into prose, here are some ways I would rewrite a few lines.
Sometimes the eye of heaven shines too hotly. Or, sometimes, it is just too hot in the sun.
The sun’s gold complexion is dimmed often.
Everything that’s fair (about a summer’s day) declines sometimes.
Death will not brag that you wandered in his shade.
Consider the line you asked about.
Every fair from fair sometime declines,
Since this is in poetic form, there is no real “normal” placement for “from fair.” In prose form, if you are sticking strictly to the rules of grammar, and keeping as close as you can to the actual line, I would write it like this: Every fair aspect from the summer’s overall fairness declines sometimes. All that’s fair from summer declines sometimes.
The poetic use of “from” makes it difficult. It would be more correct to say, “All that’s fair about summer declines sometimes.”
“From” is a subtle indication that summer is no longer present; that it has passed. This underscores the point that the memory of the speaker’s loved one lives beyond the length of the summer’s day or summer itself.