I have a S6 edge. It's display seem to be dead but internal works

It is not working. It turns on and the display will be seen. But sometimes when we restart it, it will turn on but the display would be dead especially when we put the sim. But everything is working on the inside. I even attended a call in this condition to check if the touch was complaint. Should I change the display or the motherboard. Also i want to know if i can put a 64gb motherboard in this 32gb phone. Please help me from this situation.