Tricky. It looks as if something is missing. What it says is "the reason for me to exist inside". Inside what though? A rather wild educated guess is that what is missing is "heart", "the reason for me to be/exist inside your heart". As is it is akward Greek.
then it means "içerde bulunma/var olma nedenim", reason also means "neden, sebep" besides "mantık" so I'll edit it. But it sounds a little odd, do you think it's correct this way? do we have to add "varsa" after "nedenim"?
The whole thing means, "And if you have a, b, and c, if you love me." a, b, and c are "the courage to love, the strength for true love, and the reason for me to exist inside". I translated "if you have" as "-in varsa" - I wasn't sure I needed to repeat it after each one, but I guess the last one is necessary.
one "varsa" would be enough then :
"ve sevmek için cesaretin, gerçek sevgi için gücün ve benim içerde bulunmam için nedenin varsa, beni seviyorsan"