Yes, I know the Galaxy S3 is an older phone now, but I still think it deserves some attention! When I got this phone a few years ago, it was my first smartphone. I was admittedly a little biased and thought the world of it, but things have changed since then. All technology slows down through time, but the S3 feels this in a much more brutal way. I had to replace the phone once and with each handset I had battery problems. I took the necessary actions and precautions to keep the handset in good working order, but the battery continued to fail miserably on me. With a low power battery comes an operating systems that performs at a sub-par level and this was no different. Unfortunately, the S3 started out strong, but ultimately did not withstand the test of time and because of that, I would not recommend this product for purchase.
Well, considering how fast the technology innovations are these days, it won't be long before S3 is completely phased out. Inevitably, we can expect the price of surplus S3s to greatly depreciate. We're still at the S6 generation but I have a feeling within the next few months, we're going to see S7 and S8 models. It's hard keeping up with these upgrades.
I had the EXACT same experience as you did! This was even a bit scary to read!!!! Galaxy s3 was my first smartphone as well and at first I thought it was the best phone on earth! (obviously - I had never tried another one). However, 2 years later I literally had to give it away to sell parts because the phone didn't work anymore. The battery was awful and the operating system was freezing all the time. I have an iPhone now.