A few years ago I bought Metro Theme. Now is see in Search Console over 1k errors because author and updated data is missing. Do you know how to fix this problem?
Should I edit files functions.php and content-page.php? What should I change inside the code?
Without knowing exactly which theme it is then it is hard to judge but your first move should be to make sure you are using the most up to date version of the theme and WordPress.
If that doesn’t fix it then you can try reaching out to the author but you are well outside support periods so they may no be able to help depending on what the issue is.
Lastly you could look on www.studio.envato.com for a freelancer to hire and help
Errors in search console won’t affect your rank. Quite frankly, you can ignore them. It’s only necessary for companies who want to make sure Google can interpret every little detail and number.