Apache 2.4 Enable mod_deflate on Debian 10

The mod_deflate module provides the DEFLATE output filter that allows output from your server to be compressed before being sent to the client over the network.

To enable  deflate_module typ

a2enmod deflate

Now to activate the new configuration, you need to run:

systemctl reload apache2

To compress all these files you can add deflate_module option in your .htaccess file

<IfModule deflate_module>
	AddOutputFilterByType DEFLATE text/html text/css text/plain text/html text/xml image/gif image/jpeg image/png image/ico text/javascript application/x-javascript application/javascript application/json application/pdf
</IfModule>

or use this if you don't  what to compress images or PDF files

<IfModule deflate_module>
	AddOutputFilterByType DEFLATE text/html text/css text/plain text/html text/xml text/javascript application/x-javascript application/javascript application/json
</IfModule>

Links:
Apache Module mod_deflate