ever since i did upgrade my phone randomly restarts, runs really slow, screen is jumpy and not as clear and my battery life is awful! I tried running repair asst and it says my firmware is not suported
I cache clear or factory reset might be the best place to start. You aren't the only one with these issues, which seem to plague S5 owners after every update. YMMV and some have seen success with the above steps, others have not.
will factory reset delete everything on my phone
Yes, you'll need to back up beforehand.
