I accidentally deleted some important messages. Can they be retrieved

You basically have two options for recovering SMS texts:

1. Potentially from a backup of your iPhone that was made when you send those texts, and/or
2. By contacting your cellular voice provider to see if they offer a means to recover deleted texts.

What kind of messages? iMessages, SMS text messages, eMail messages, or something else?

I totally understand. I still ask my kids for help when I have iPhone questions. ;)

To help you get started, here are a few helpful links:

• Skills: Getting Started with iPhone - Apple
• iPhone User Guide - Apple Support

If you have an Apple Store near you, they may still offer "one-on-one" sessions to help you get familiar with iPhone.