Green screen of death on iphone 6s

how can this be fixed? Whats wrong with my iphone? I had an i phone 6s 2 years ago for about 2 years and i got this green screen of death that started randomly flickering on and off myphone and shutting it sown and eventually after a month or so of it happening more frequently it green screen came on and never ended up going away and now the phone wont even turn on. After that i was forced to buy another phone which i bought the same phone the iphone 6s right from the store and it hasnt even been 2 years since that happened that it started to happen to this phone now to and i am worried because i dont wanna loose evrything again or buy a new phone now with s prices. Does anyone have any info on this screen?