What skill needed to fix broken WordPress site after theme update?

I need to find someone to fix my site. What skill does the person need according to my problem below?

My theme is SEO WP, a premium theme I bought from Envato. I updated it, together with the plugins, and then started having issues. I contacted my web host who helped to some degree, but the big problem I have right now is that in the dashboard, my site will not allow me to actually do anything. I can move around but for any action I take, it simply “thinks” and that’s that.

It is showing code right at the top that my web host fixed but it returned. They say that its the mega menu plugin that’s broken the site, but I can’t get support for it.

Also, when I want to edit a published post, there is nothing in the post, although at least it still shows on the front end of the website.