I have written my corrections in yellow. Hope this helps :)

1- Silence please.."I will now hand out the exams."

2- Take the mobile off the table. Keep it into the “school bag” o “rucksack”.

2- Remove your mobile phone, any notes, and put them in your school bag.

3- Take your notes off the table.

4- You have to write down the name of your profesor in the gap. 

4- You have to write down the name of your professor in the gap provided.

5- “You can turn the exam over” o "You can flip the exam".

5-  “You can turn the exam over” 

6- I can't answer any questions about the exam, you will have to ask the professor.

7- If you have any questions you have to wait until the professor comes to the classroom.

7- If you have any questions, please wait until the professor comes to the classroom.

8- You can't leave the classroom until half an hour from the begining of the exam. Why?
Because another student can come to do the exam and if you leave the classroom
now you could tell it the questions.

8- You may not leave the classroom until at least 30 minutes after the exam begins. 

9- “You have 45 minutes extra of time” o “You have 45 more minutes”.

9-  “You have 45 more minutes."

10- When you finish the exam rise your hand and I’ll go to collect it.

10- When you finish the exam, raise your hand and I'll come collect it.

11- You can go to the bathroom only during the break.

12-- If you have any problem you have to tell it to the professor.

12- If you have any problems, please report it to the professor.

13-- You can borrow the typex from another classmate.

13- You may borrow tipp-ex (white out) from another classmate. 

14- - Could you lend her your rubber please?

15-- If you need a piece of paper I can give you one. You don’t need to give it to me it’s only for rough draft.

16- - If I put you a mark on your exam the profesor won’t grade you. <-- I am a little confused with this one.

16- If I put a mark on your exam, the professor won't grade you.  

17- - Do not separate the exam sheets. or Keep your exam sheets together.

And Could you explain me the meaning of this sentence?
-Hand is stapled together at the end of the exam.

I have never heard of this expression but I think it means after students finish the exam, they must keep their hands together (not allowed to use pencil, phone, or anything). They have to remain quiet and not do anything until the exam end time.