Google Change of Adress question

Hey everyone,

I have an older website with a bit of content that already had a few backlinks and rankings, but I want to use the content for my new website instead and keep the rankings (same niche). I used a 301 redirect for every blog post and the home page, and informed google of the change of adress via Search Console Settings

now my question is, do I have to remove the blog posts from my old website? Or do I just keep them AND have the same post on my new site as well?

I really dont want to get flagged for duplicate content, but I also dont want to lose my initial rankings

Would appreciate any help

Your old website (domain) even does not need to be hosted. You should do page-page 301 redirection.
Google (and visitors) will see the content of your new site if visits old site's URLs.