Q: why is my app store downloads so slow?

Product: IPhone 6 Plus 16 GB,iOS 9.2.1

My app store downloads are very slow.It was good before.But works good on cellular data butnot on Wi Fi. A 100 MB applications takes about 1 hour but before it would take 10 to 12 minutes.

I've tried everything i found on the internet like changing DNS server,resetting network setting,factory resetting the device,changing network but still nothing has changed in the download speed.I have a decent internet speed of min.1 MB and can go up-to 10 MB.Before I had the same problem and got fixed when i switched the network now nothing works.Is there anything that can help me?