If you are interested in restricting your download speeds, you can do it by following this quick tutorial.
Please note that this only works on Mobile Data and not WiFi.
This is one of the few ways I found to limit the data speed and no root is required!
There are many reasons why you want to reduce data speeds, maybe you are concerned that you will run out of data quickly or maybe someone else is using your phone and you don't want them to eat all the data that you have.