Emails say message not fully downloaded from server

Hello Reileene,
I understand that you are not able to read your email as it tell you that his has not downloaded from the server. Let's see if we can get that working for you.
Double press the Home button to bring up the recently used apps and the swipe up on Mail. Once it is closed, open Mail again to see if the message loads. The reason for this is if Mail is not responding to your request for refresh, then you will want to close it out to get it working again.
Force an app to close in iOS
https://support.apple.com/en-us/HT201330
Take care