IPhone 4s running really slow?

So my parents stopped letting me have my phone and iPad in my room at night so I resorted to my old iPhone 4s to keep me occupied. This hasn't worked out too well because my old phone takes 10 minutes to load 1 minute of video and will never continue if it has to buffer. I've tried re installing YouTube so it is not the app. I haven't used this phone for about a year. Anyone know why it is so slow and how I can fix it?

If you believe your iPhone and iPad have been getting slower over time, you're probably right. The decline in speed happens so gradually that it's almost imperceptible, but one day you realize that your apps are responding slowly, menus are sluggish, and Safari is taking forever to load simple websites. In this article, I'll explain the real reasons why your iPhone is so slow and show you the fixes that will make your iPhone, iPad, or iPod run as fast as possible.
1. Your iPhone Is Out Of Available Storage Space

Like all computers, iPhones have a limited amount of storage space. The current iPhones come in 16GB, 64GB, and 128GB varieties. (GB stands for gigabyte, or 1000 megabytes). Apple refers to these storage amounts as the iPhone's "capacity", and in this respect, and iPhone's capacity is like the size of a hard drive on a Mac or PC.

After you've owned your iPhone for a while and taken lots of pictures, downloaded music, and installed a bunch of apps, it's easy to run out of available memory.

Problems begin to occur when the amount of available storage space reaches 0. I'm going to avoid a technical discussion at this point, but suffice to say that all computers need a little bit of "wiggle room" to keep the software running smoothly.
Head to Settings -> General -> About and look at the number to the right of 'Available'. If you have more than 1GB available, skip to the next step - this isn't your problem.