Where can I find places to learn how to repair cell phone or open my repair center?

There isn't anywhere to learn how to repair cell phones since most (like 98.%) aren't repaired anymore these days; they are simply replaced. Cell phones currently all use surface mount components, which means parts can't be easily replaced from their circuit boards. The days of discrete, separate components are long gone. Additionally most cell phones and their inner components are manufactured in China on robot machinery and therefore the vast majorities of the parts are not even available here in the US (or anywhere else) anyway. Nor are the schematics and technical diagrams to examine how they are designed and then determine how to repair them. There is no provision whatever for repairing them anymore. Also, since the price of cell phones is so low, they have become disposable, even with the most expensive models. It's WAY cheaper to ship the customer a new phone than to repair or rebuild. What carrier wants to take in an old phone, ship it to the manufacturer, have Samsung or Motorola chase down a defective transistor or diode, replace it, put the phone back together again, and then ship it back? They’d be out of business in months, maybe even weeks if they offered to do this for their customers. The last phones that anybody tried to offer repair on were the Motorola 'Flip-Phone' Micro-Tac models of 1987-89, and those had to be shipped to Motorola for service. That's why you'll find trash bins at Office Depot and elsewhere with signs on them saying 'deposit cell phones and empty printer cartridges here.