The time it takes for Google to read and process a sitemap can vary based on various factors such as the size of the sitemap, the frequency of updates, and the overall crawl budget allocated to your website by Google. In general, Google aims to crawl and process sitemaps promptly, often within a few days to a week after submission.
However, it's important to note that Google doesn't guarantee immediate indexing or crawling of all URLs listed in a sitemap. Some URLs may be prioritized over others based on various factors such as the authority of your website, the relevance of the content, and the frequency of updates.
If you've submitted a sitemap to Google Search Console, you can check the status of your sitemap and monitor indexing progress over time. Keep in mind that regularly updating and maintaining your sitemap can help ensure that Google crawls and indexes your website's content efficiently.