iphone when is it time to update

[car10002]

Hi

Got a iphone4 and Was wondering if there was anything that can be done to the phone to give you more time to save up to get a new phone and upgrade to iphone6 or even a bit then laybuy at local phone shop. If it helps you the phones doing following.

Replaced battery once and was better and now back to not lasting quite a day.

Phones very slow on internet in some areas and doesn't seem to work as well as the iPhone 5s onwards.

Phone sometimes shuts down out of program you're in.

Phone sometimes freezes in certain program's and the iphone4 was fastest you could get when new but is getting slower and slower.

The top power button is hard to push when pushing it to lock screen.

Had phone for over 2 years and wondered wether there's anything that can be done to give more time to get a new one.

Thanks