How to make Sitemap.xml correctly?

Question

Search Engine Optimization

There is a project with many pages, in fact, here it is - web-payment.ru
The task is to make a Sitemap.xml for it for search engines, because. the site is constantly updated, then it is necessary to generate a sitemap on a regular basis, but how to do it correctly?
Seoshnik recommends this method:
The sitemap is constantly supplemented with entries until it fills up to 500 urls, then when each new entry is added, the first url is thrown out of it, which has not changed in any way over the past month (for this, a flag is put on the page, which is reset to zero with each comment and every day accumulates 1 unit.The url with the maximum flag is thrown out of the list)

Answer 1

Why 500? The limit is 50k URLs per file, the index file can contain up to 1000 links to regular lists of URLs, for a total of 50 million URLs. This is more than enough for 99.99% of sites.
www.sitemaps.org/faq.html
help.yandex.ru/webmaster/indexing-options/sitemap.xml

Answer 2

One of the best tools for XML is codebeautify.org/xmlviewer XML formatter, XML validator, XML minify, XML to JSON, XML to CSV

Answer 3

I did not understand the question.
You select all the entities that should be in the sitemap.
You generate urls for them.
You set changefreq, lastmod and priority
If there are less than 50.000 records, then we simply display the data in a loop.
If more, then we calculate the number of files at 50,000 entries per file, generate one file with links to other files, in an additional folder, for example sitemaps, generate files at 50,000 entries per file.
Something like this.