Normally, when a user or Googlebot try to connect a website page that does not exist, the not found errors (404) will display in your browser.
In normal situations, errors (404) will influence the ranking of your website, and you must assess these errors as soon as possble. There are some tips can help you investigate your websites:
The default 404 error page is a very important part of websites. Creating a custom 404 error page can make the user experience better. You may never control all of the links to your website, or solve all of errors 404 that listed in Search Console. The recommendations are check and solve the top-ranking issues first if it is possible. And leave those errors 404 that not related to your website ranking.
When you delete or rename a page from your website, make sure you move all contents to another page, or you may not need this page anymore. It is also important to set up the appropriate re-direct. If you rename a website page, make sure you redirect the old URL to the new page. When users connect to the old page, the system will automatically transfer users to the new page. If you want to delete all the contents of your website page without putting new contents to replace it. Make sure the old URL return a 404 or 410. Because Google treats 410(gone) the same as 404(Not found).