The error message indicates that your hoster has switched off the email functionality in PHP. You have 3 options for a solution:
a) You contact the support of your hoster and ask them to activate the mail function.
b) You use a plugin such as https://www.ads-software.com/plugins/wp-mail-smtp/ to send the e-mail via an e-mail server specified by you in the plugin. This would also be my recommended method as it ensures that emails from your WordPress reach the recipient safely.
c) Ignore the email issue and change the admin email in the database directly. To do this, you need access to the database. Your host can certainly provide you with this. In the database there is a table called “options” (preceded by your project-specific prefix) and a data record with the “option_name” “admin_email”. You can change this here without having to send any emails.
