Francisco is a man in his 55´s (or so), with a silver-hair mane.
If he has a profuseness of hair - and thick ones- if not you could describe with "with a thining gray-hair" (whitey), silver (a bit white-bluish ring to it), or grizzly (granny-whitey) etc.
Or other descriptions:http://www.macmillandictionary.com/thes ... ts-of-hair
He is graduated in Physics...
The way it was, there´s no link betweent both things his hair, and the fact of having such academical title, perhaps you might have stated "Francisco is a man in his 55´s (or so), with a silver-hair mane who graduated in Physics..."
Plus, the way you made the statements it made one think of the "hickup" effect. When someone use so much of punctuation, that one has to make many "stops" to the point of getting tired when reading. I suggest that when one is making his proofreading read it aloud as well, it helps!
He wears [u]round glasses[/u]
 all the time, [wire-rimmed, or plastic rimmed? just glasses or sunglasses?) , that soften his squared/angular face and convey him a vintage look . However, it doesn´t prevent him from showing reddish/blooshot eyes those dark circles around them.
He uses a light green (knee-lenght) coat/apron  with some kind logo of the institution he is with/he works to (also - lab/company logo/department logo, etc) in the pockets. (maybe sewed/stitched/painted or simply on the pockets, as you wish.)
 or...psychedelic, or still achademical/serious look, what you have...
Those kind of glasses are to give that effect, so I did not need to say they are circular and small.
 white coats are usual with medicine stories, even fictional ones, but then ''light green", just not to change your initial "script".
Then, you fall in the punctuation trap (hickup effect again).
Well, I it´s getting late here. I will get to you again, or maybe somebody else...the thread is open, then.
Luiz, I can see that you expresses well in Portuguese and is a brave guy, brave enough to put your writing to the proof.
You are a promising talent, and certainly, with some effort and hard work you will get there!
Your text form was "a narrative" if I understood well, good, but you lacked some connecting words (later on, after that, then, next...etc).
You had a difficulty with verb tenses, at a certain point you used present forms and then, all of sudden it turned into past form (more notably in the Portuguese version).
Overall, you was on the topic, the ideas enhanced the main idea, you just need not to overlook details (see the new information I brought up?) they enrich your text and make the reader understand easily, teachers are busy, and the general reader lose interest so fast! you have to get good hooks.
You need to get the reader attention!
Again, you are off to a good start! Just work hard. See you around.
Wow, Telma beat me to it!
ha ha ha.