Hello! My iphone won't turn on. How can I fix it?

My iphone 7 plus red edition has an apple logo looping issue. It won't turn on anymore. Upon charging it the apple logo will just show up for a second and the turned to black again. I went to an Authorised Service Center, they did a hard reset but it's all the same. They said to me that the lifespan of an iphone is only 3-5 years but mine didn't even reach 3 years.