iphone 5s reboot red screen

Hey

I have iPhone 5s that has some serious problems unfortunately. Has been working years with no problems till now.

On the evening on 10th July, while useing camera and flashlight all problems started. At first phone just turned off and would not turn on until i plugged the charger. Then it started and worked few times like this at evening.

After few crashes like that my iPhone 5s i completly gone mad. Only keeps rebooting. Appears Apple logo for about 15sec and then sometimes red screen sometimes black screen and then againg Apple logo.

At first i thought battery is dead after 3 years but today replaced battery and same thing happens.

Can anyone give me some information if there is any way to repair my iPhone. Not very happy to get a new iPhone for no reason. Or at least would like to get some info what might have caused it? Can this be a software problem cause i updated to latest version not long before this crash thing?