Hi Chali.666,
Welcome to Apple Support Communities and congrats on your new iPhone 7. As I'm understanding, it you're experiencing some issues when trying to set up another email account on your new device. I understand the importance of being able to have and quickly access your emails on your phone so I'd be happy to help get this issue resolved.
Let's start by closing all running apps in the background, shown here: Force an app to close on your iPhone, iPad, or iPod touch
Next, check out this article with steps to Restart your iPhone, iPad, or iPod touch.
Lastly, let's try adding the email account by following these steps provided here: Set up an email account on your iPhone, iPad, or iPod touch
Please feel free to let us know if this helps or if you have any further questions and I hope you have a wonderful weekend.
Cheers!