Amazon Linux AMI Apache User and Permission Web Directory

I have a AWS ec2 instance with Amazon Linux AMI running. As the web server I installed Apache and the web directory is /var/www/html. Until now I had the permission for /var/www/html set as 777 under the user c2-user (chmod -R 777 /var/www/html). I read, that you should usually have set the 644 permission for web access. But as soon as I do that, I get the "403 forbidden" error message. What do I have to change? Thank you for your answer