iPhone 5s malfunctioning - BSOD and/or Apple Logo Loop

Hello AppleManiacs,

I am an AppleManiac myself!

However, I've been facing some issues with my iPhone 5S. I have it for a few years, and lately (after the iOS 9) I've had the Blue Screen of Death problem twice, and now an Apple Logo Loop on startup. For both cases, I needed to perform a forced Reset and Restore (plug it to computer + iTunes > Hold Sleep/Shut + Home Button until Recovery mode is on).

1. When I had the Blue Screen of Death (BSOD) issue, my iphone started crashing (sudden shutdowns) and slow performance (crashing apps).

2. And when I had the Apple Logo Loop, just before I restarted it, all my contacts disappeared.

Is it a software or a hardware problem?

I bought this iPhone in London, but I currently live in Brazil.

How does it affect the support and warranty for my 5S?

Although I'd love to buy an iPhone 6S, due currency conversions (USD > BRL), it's not viable anymore.

Kind regards,

Felipe Y. G.