Trying to think how I would handle this one myself, seeing that dc know perfectly well that my own very happy marriage was a result of a teen holiday romance 31 years ago
. The difference being that I had excellent English and was able to get to know dh through long letters, that I finished my education before I actually moved, and that dh was happy to spend that time saving up for our life together. Basically, that we were that little bit more mature than this couple.
I think what I would say is something along the lines of:
"Yes, I do understand that you are in love and I do believe that love at this age can be serious and forever. However, I do not see why you have to be married straightaway. Marriage is a longterm commitment. If you are both serious enough to be contemplating a commitment that might last for 80 years, then you can wait another two years before you start it. That will help you to plan things properly and give a better chance that things will work out longterm for the two of you.
If he is serious about wanting to support a family here, then he needs to learn better English in that time. If you want to be his wife, and do your bit for your family, then you will be in a much stronger position if you finish school before you move in together. If you want to live with him in Turkey, then you need to learn Turkish.
I will not give my consent for you to marry him or anyone else before you are of age. I love you and I understand you, but I will not put my name on something that I think is not in your best interests at the moment. But if you are still together and working towards a future in two years time, then I will be very happy to give you a nice wedding."