And the directories thereunder?

Also note that 777 is a one-big-club-hits-them-all "solution". More fine grained permissions may be possible, see [Forum, post 183419 by erAck in topic 31993] What are the correct permissions for Piwigo files and directories ?.

You are not trying to tell us that you are running a web server as root, are you? If so, do yourself a favour and shut it down. Now. Or did you "just" unpack and install Piwigo as root? Don't either. Use a dedicated user account in group with the web server group account, or after installation recursively change group of everything to the web server group, and also after installation give that group permissions rwx on directories and rw on files. Or use the web server account or if you have no clue then use the Piwigo netinstall package https://piwigo.org/guides/install/netinstall and point your browser via your web server / domain to the piwigo-netinstall.php file which installs files and gives them the initial ownership and permissions of the web server user.

I finally solve the problem with below command

curl -o piwigo.zip https://piwigo.org/download/dlcounter.php?code=latest
sudo unzip piwigo.zip -d /var/www/html
sudo chown -R www-data:www-data /var/www/html/photo/
sudo chown -R 755 /var/www/html/photo/
cd /etc/apache2/sites-available/
sudo cp 000-default.conf piwigo.conf
sudo nano piwigo.conf
   DocumentRoot /var/www/html/photo
   ServerName www.kevincaermas.com
       <Directory /var/www/html/photo/>
       Options +FollowSymlinks
       AllowOverride All
       Require all granted
       </Directory>

sudo a2ensite piwigo.conf
sudo a2enmod rewrite
sudo systemctl restart apache2.service

erAck, thank you for advice and support.