The way you pose the question is a bit unnatural. In Arabic, it makes more sense to ask 'will you stay loving me' than it does to ask 'will you love me forever'. So, a better phrasing of the question would be:
هل ستبقی محبا لی للابد؟
Will you stay a lover to me for eternity?
It is not the best phrasing, mind you, just a better pharsing. It still feels awkward and wordy, but it is the best I could come with on the spot. Perhaps somebody can offer a better version.
Assuming you are not sociopathically cruel, your answer would probably be on the lines of:
Sure.طبعا
Of course.بالتاکید
Or even better:
I will never stop loving you.لن اتوقف عن حبک
Adjust final vowel to the gender of your beloved.
