Thanks for your comment!
can you please write more about the security issues? I opened some ports in order to use some of Server's capabilities` how can I make it safer?
Opening up a port is always a risk. You're basically punching a hole through the firewall. If the service listening on the port has a vulnerability, it could be used to hack into the server, and from there potentially to other machines on your network. Usually it's highly recommendable to put the server in a DMZ (a separate network that is isolated from your local network). You should also turn off all services on the server that you don't need to access remotely, particularly admin web interfaces. If you have a high risk of targeted attacks, you might also consider running an IDS (intrusion detection system), but this can get rather complex.
These are not just theoretical risks. The Internet is a very noisy place these days. If you monitor the traffic arriving at your router, you will probably see port scans every few seconds ...
the firewall on the server is working (I excluded the Server app) and the firewall on my router is turned off. Should I turn it on?
It really depends on your setup, but broadly speaking turning off the firewall on the router is a bad idea since it potentially leaves all your other machines vulnerable.
This is a complex topic that cannot be answered in a few forum posts. If you don't know what the above means, I'd recommend to use a cloud service instead of your own server if the information you are storing is in any way sensitive.