constant IMAP issues when using mail on my iphone

My email on my iPhone which is set up as IMAP account (with all correct UN, PSW, port, etc and 3rd party app is enabled in my Xfinity mail account) is constantly loosing connection with IMAP server.
It may work for few days and then it stops. Xfinity support suggested to use the Xfinity app but that app is not user friendly.  Please help !! can not work like that