Set root permissions for users for www-data group
Give writing rights/permissions for www-data and add yourself to www-data group.
The directory with site: public_html, user that will upload: user1
# at the beginning means you're root. If not use sudo.
# chown -R whatever-user.www-data public_html
# chmod g+w public_html
# usermod -a -G www-data user1