https://linux.die.net/man/1/chown
but be carefull, chown can also destroy a lot.
chown user:user /home/user/web/domain.tld/public_html -R
chown user:www-data /home/user/web/domain.tld/public_html
Should to the job. But be aware, usualy you should know this while using hestia: Please read this, before you start!