If a village is nearby, the zombie will target a villager and attempt to take the shortest path to one unless they are attacked by something else. Zombies will attack wandering traders as well. They will also target iron golems which protect villages. If a player is wearing a zombie head the aggro range for zombies is reduced to half.

Detailed information available - Minecraft Zombie | Minecraft Cartography Table

There are several ways to get a wet sponge in Survival mode.

1. Find them Growing in the Ocean Monument. You can add a wet sponge to your inventory in Survival mode by gathering wet sponges that grow naturally in the Ocean Monument (also called Guardian Temple). ...
2. Find and Kill an Elder Guardian.

More information visit - Minecraft Sponge

Reboot your device as this can do the wonder in most of the cases. Uninstall and Re-install the application on your device. Check the IMAP/ POP Configuration Settings in Android. Make sure your phone is connected to the network.

Detailed information given on that - SBC Email Help