Why does minecraft pocket edition lag loads when I'm connected to Wi-Fi?

Every time I play mcpe connected to the Internet it takes ages to load up the game and crashes really easily. Like earlier today it took almost 10 mins just to get on the title screen. But when I turn the Wi-Fi off ithe works normally and dosent crash. This happens to all my friends when they connect to my Wi-Fi as well. I've tried closing all my apps, I've tried turning the Wi-Fi off and on again. Nothing seems to be working. It's definitely something to do with the Wi-Fi. Can anyone help?