Hi there,
In your source, I’m seeing this as your description: https://www.screencast.com/t/EokWPJgO
That’s coming from Yoast.
In Google, here’s what I’m seeing: https://www.screencast.com/t/UqP7Ndjkq80
Seems to match?
GeneratePress itself has zero functionality when it comes to your meta descriptions/keywords – those are plugin-territory options that a theme shouldn’t touch.
I don’t know what your last theme was doing, but it shouldn’t have been doing anything SEO-related.
When it comes to your organic traffic – GeneratePress (or any theme) won’t have a huge effect on this. Your content is the #1 factor when it comes to SEO, not your theme. The only thing a theme can do is ensure that your site is loading as fast as possible (from the theme end of things).