Template creation and content adding via backend

Dear WPMUDEV-Team,

I'm new to wordpress and a total beginner. I've got two questions at the moment and struggle to find an answer:

1. Let's say I create a nice view for a certain page on my website and I want this design to become a standard/my template for future content. How can I create a template from that that I can fill with content from within the backend? Is that possible? Do I not extra plugins? Is there a backend designer plugin as well? How is it working? I hope you understand my question...

2. Is it possible to add a third party plugin plugin like for instance the filtering plugin FacetWP?

Looking forward to your answers. Thanks a lot in advance. Best,