Hi,
I`m beginner in this and want to access to device on LAN side through USB 3g modem.
I setup modem and get internet access on all LAN ports.
Tried several tips for port forward in NAT but useless.
I update my public IP from provider.

Can You help me how to do it and what to check.

Best Regards

Stanko

If you have a routable Public IP address from your ISP. You need to check if it have open ports and their are visible outside.
You can use this
http://www.canyouseeme.org/ or other page instead.