Question: How long does it take before changes you make to your page title and description are updated on Google

Changes to your site, including edits you make to your page titles and descriptions, do not appear in search engine results right away. Google must re-crawl your page in order to see that the saved version in its index has been updated with new content. 

It is important to note that Google crawls and indexes content that it feels is the most appropriate. The page titles and descriptions you add to your site are just a guide for Google; If Google finds something it likes better it will add that to its index. This is why the same site may look different in search results on desktop and mobile.

To ask Google to re-crawl a specific page:

If you want to ask Google to re-crawl a specific page of your site, you can use Google’s URL Inspection Tool. To use this tool with your website, you must first create a Google Search Console account and verify ownership of your domain.

Read more about Google URL inspection tool: https://support.google.com/webmasters/answer/9012289?hl=en