What's the problem with you?

You can add another web part by clicking "Add a Web Part" button as your screenshot.

What's the problem with you?

You can add another web part by clicking "Add a Web Part" button as your screenshot.

Update:

If your page is in Site Pages library, you can go to SharePoint Designer->Site pages in the left pane->find the page and Edit File in advanced mode.

Add insert Web Part Zone via click the botton: