Installed new version, need guidance

Hi,

I installed the new version and I ran into the following issues:
1. Pagebuilder disappeared along with my custom templates
2. My custom pages no longer show the custom templates (just shows template number)
3. My child theme no longer works (looks like a lot of new configuration changes)
4. My custom menu does not work/function as it did before
5. I’m getting the fatal 404 error when I click on any menu items/categories

Can you provide some guidance on how to resolve each issue. I like the new look, but, it seems like I’m going to have to go through and reapply all the modifications again. I don’t want to lose my custom templates.