This seems a bit vague. There are a few of these 5.1 ZTE phones. Do you happen to know which model? Or maybe a model/serial number, under the battery. Long story short you need a new digitizer. It's either been broken from damage or from liquid. If you give us more info, we can supply you with a guide and parts. You also may want to contact your cell provider, and find out what kind of warranty or insurance you may have, to weigh your options