Existing SSL certificate conflicts with a new one

Hi,

I just started to learn Linux server and tried to make a web site using WP. So I installed a LAMP on VPS and WP on it using Digital Ocean tutorials. Got my Let’s Encrypt SSL certificate for mydomain.ee.

To avoid problems I decided to make a dev. one web for mydomain.ee. Made a copy of existing config:

$cp -p /etc/apache2/sites-available/mydomain.ee /etc/apach2/sites-available/dev.mydomain.ee

Made another wp dir. using the same command:

$cp -p /var/www/mydomain.ee /var/www/dev.mydomain.ee.

And also I got a new SSL certificate for dev.mydomain.ee. So before I did this, dev.mydomain.ee worked very well, but now, when I want to go to dev.mydomain.ee it says:

Forbidden

You don’t have permission to access this resource.

So the question is how I can get rid of the existing certificate to get a new one?

Tell me if you need more information

Thanks!