Galaxy s5 sm-g900p looping and apps crashing

Hi everyone,
I'm very new to the forum and I'm in need of your help.
I purchased a galaxy s5 from someone on gumtree and I'm having some problems.
Originally it was running g900pvpu1boa6 Sprint, however all the apps started to crash, the keyboard was crashing, the google play and many other random services.
I tried to install the latest sprint firmware g900pvpu3bog1, that worked however the same problem still occurs. I tried to clear the app caches and still it wouldn't work. Finally I followed some instructions and I wiped cache partition. But it started to loop on the Bootup. I took the battery off and it eventually booted into the phone but same problem exists. The phone is not rooted from my knowledge.
What should I do ?

[HELP][I9500] Different infinite looping!

Guys, I need your help, I'm brazillian and my S4 broke, sorry for the bad english, he have android 5.0.1, I was wearing normally and suddenly restarted, and the infinite loop start, but can not open the Recovery Mode, and in the Download Mode the smartphone restarts regardless of the option that I choose, he dont have a root or a personalized room, its has factory settings, the only thing that happened was strange when the battery is low on charge and I open the camera application sometimes causes a shutdown, there Odin method but the problem is that smarthphone does not enter into Download Mode for I make it, help me!