Dns change issue

i have added two NS to my domain name and create two A record For both name server. both A record are two ISP ,

When one NS down means when one A record down automatically sites not working or redirect to next A record

Your question is not quite clear.

Also, please pay particular attention to https://community.cloudflare.com/t/please-read-me-first-what-to-include-in-your-post/103270.