I recently bought my Minecraft on my iPhone 7 and wanted to start it but after the mojang loading image it just turns white and Minecraft will not work for me.
This is a bug known to Mojang: https://bugs.mojang.com/...MCPE-35078
Many users complain about it:
https://www.minecraftforum.net/...ite-screen
Apart from re-installing the app, you will not be able to do much there.
Thank you just noticed when you start that does not work with the Wi-Fi. Say wlan to Minecraft is not (white screen) mobile data and wlan from Minecraft works