Take a proper repair phone set course. Certificate is important nowaday.

Last time i heard an interview from Ai.FM with local repair academic founder. He said repairer is very high demand especially in Middle East and US.
His always receive many enquiries for repair technician recommendation.
He also said Phone technology is fast pace and the academy school also must keep on the pace technology.
He add on don't bother about new phone technology yet because all still under warranty. Learn how to repair model which released 2 years ago.