Advice:
IF you now not yet have a clue at what you are doing, and you want to experiment: write down what you do, the exact changes you make. When something does not work, or you make mistakes, you know exactly where the mistakes happens and how to return to normal.
And always work in a test environment. In linux that is easy.
https://geekflare.com/linux-server-local-dns-caching/
We have discussed this issue of DNS several times on this site, examples:
https://greatawakening.win/p/12jcY8BZ7D/dns-errors-shutting-down-major-f/c/
https://greatawakening.win/p/12iN7L273w/if-there-were-to-be-an-internet-/c/
https://greatawakening.win/p/11RhhjOPOK/if-you-are-using-google-dns-8888/
Now more than ever, learn how to use solutions to your advantage. Read carefully both posts:
Advice: IF you now not yet have a clue at what you are doing, and you want to experiment: write down what you do, the exact changes you make. When something does not work, or you make mistakes, you know exactly where the mistakes happens and how to return to normal.
And always work in a test environment. In linux that is easy.