Can we have a girlfriend or boyfriend?

A friendship with the opposite sex is not of Islam. It used to be of the Jahiliyyah (pre-Islamic era) style of life. 

A friendship of the two sexes can never be safe or sex-free. I agree that in some exceptional cases, it could be innocent. But, a law is usually amended for social regulations. There is no law to be customized for a certain person or few people.

The Qur'an and Sunnah guidance for the sexes dealing with each other has a main major issue for which Islam has set principles and rules to govern. It is the desire and lust. The Qur'an prohibits anything that motivates one's heart in a seductive way towards the other. The Qur'an tells a woman when she speaks to a man to speak in a way that doesn't show any interest in him lest he should feel seduced to build up an unhealthy relationship. If there is a possibility in any kind of action that it could lead by some percentage into catastrophe, no one will ever take that risk. I can say what you call friendship could have some percentage of leading into haram. How would you go to that risk whereas if a doctor says to you an operation of a certain organ could lead you into death? You would say I don't want to risk my life, but I will take the pain.

Firstly, this is a deen but not a man's opinion. Lastly, if you take it, you certainly will be on the safe side. If you want to follow reason, reason has a lot of defects and sometimes we cannot draw the line to know who is sane and who is insane. Sometimes you cannot know which is which.