Is the problem a slow Phone or slow internet connection?
You can test your internet speed on different websites.
If you Phone is slow you can try clearing cache or factory reset like the previous person said.
Also take a look in the settings at the applications that are running, maybe some of those can be stopped
if your Phone uses a sd card you can try to remove this and see if it makes a difference. If your sd card is full of junk or bad data this can sometimes make the phone very slow.