Does your friend know Arabic? Has he ever read the Quran before?
No Muslim on earth doubts that it is not permissible to take boy/girl friend as this leads to fornication.
Allah says in the Quran: do not approach or come close to zina (fornication).
He didn’t say: do not fornicate. He said do not come close to whatever makes you fall in this sin.
Taking a girlfriend is the evilest way and one of the means to falling into fornication.