what can i do if my itunestore is not working

I'm not clear on what app you're using. iTunes U was discontinued three years ago, so if you're still trying to use that app, it's not going to work and you can just remove it from your iPhone.

If you're using the standard App Store or Apple Music or Apple TV app, try just restarting your iPhone. If that doesn't help, post back with more details, including the version of iOS your iPhone is running and what country you're in, and someone can probably offer additional suggestions.

Regards.

That looks like iTunes U, not the iTunes Store. Try the Music app.