Domain name for my PC: how to (tried No-IP, DuckDNS and ngrok)

I want: ping server on my PC by it domain name from remote.

I have:

1. DynDNS services DuckDns (or No-IP, config in no-ip is even harder). It gets me an IP 94.154.220.216 and (sub)domain http://my_domain.duckdns.org. To configure DuckDNS on PC I need just specify some token and my domain name (my_domain).
2. Also I've launched server on lacalhost:3000.
3. Also when I go to CanYouSeeMee it says that my IP is 94.154.220.216 (that's good).
4. And I configured static IP for my PC (let's say 200.300.1.15)
5. And Setting port forwarding for with help of Port Forwarding Wizard (Port=3000, Protocol=TCP, Internal IP = 200.300.1.15)

Problem: I can't get neither http://my_domain.duckdns.org nor http://my_domain.duckdns.org:3000 from remote.

Assumption: I assume that troubles are in router configurations.

Questions:

1. How can I check what is wrong? Means whether DuckDNS doesn't redirect request to my router or my router don't redirect request to my PC.

My local network scheme:

Internet <==>    1st Router   <==>             My PC
                 static IP         static IP: (let's say 200.300.1.15)

I wasted lots of time with No-Ip and DuckDNS. They all claims they're as easy as possible, but that's not the truth. Finally instead of configuring my router and having lots of hemorrhoids with God knows what, I used ngrok - 30 seconds and vu a la! All you need to do is:

1. Download
2. Run it: ./ngrok subdomain=<your_domain_name> <your_server_port>