improve WordPress site with Divi

The goal of the project is to take an existing WordPress site and make it very easy for me to update any page with the Divi builder. The immediate need is to convert the Home page of the site to Divi.

The problems I face:
• I am a novice in WordPress and need to make frequent updates for a client
• I inherited the site from an agency and it appears that some pages use the Divi builder while others do not
• I have a request to make changes to the Home page but it appears it is not using Divi (I can't open the builder like I can on other pages on the site)
• Generally, I am not sure how Divi was implemented by the agency

I'd love to find someone who can solve my immediate problem of being able to update the Home page for my client. Ideally, then we'd have an ongoing relationship for further help on this WordPress site (e.g., making every page easy to update with Divi, safely update plugins and WordPress version, make other custom updates, etc.).