HI! Anyone can recommend where can i buy New, sealed iPhone 6 (Malaysia set) in KL or selangor? Don't want refurbished set.

My iphone 6+ is running kinda slow and sometime will hang abit. Running v11.2.1, this is 64GB model, and i have 45GB available storage. Anyone can advice how to make it run smoother, fast and better battery lifespan?

I havent change my battery yet. I cant afford to wait 3-5 working days to change it at Machine/Switch outlets. I decided to change it at Itworld where they can fix it on the same day, but currently no stock for ip6+.

But even thought if i have change the battery, the phone is still running slow right? It wont make it perform better. Correct me if im wrong.