Why is my iPhone so slow?!?!?!?

[Miranda]

I have Facebook, YouTube, id cap that, and soundhound. 4 apps. About 100 pictures. I backup my phone all the time and delete the pictures. 4.9 gigs used. 1.5 available. Good wifi connection. My iPod does this too. My laptop is pretty slow too... But my families phones go super fast and stuff. I did a speed test and it was like 4.5 mgps or whatever. I always close my apps. I also have 200 songs on iTunes but it doesn't take up much space. Tell me why my phone goes so slow?!?!:c I went into apple a month ago and got a new one over warranty and it was fast and stuff and now it's really slow. .-.