Upgrade website & Debug Drupal 7 to 10 + php 7.4 to 8.3

I have a website running on Drupal version 7 and PHP 7.2. I need to upgrade it to the latest version of Drupal, update PHP 8.3, and debug all issues and errors which appears. Additionally, the contact form on this Drupal website is not sending values, so this also needs to be fixed. Ultimately, I require a fully functional website without errors while retaining all existing functionalities. Its just background technical update + fix form.