How to access a network with dynamic ip? vpn?

Question

VPN

At the dacha there is a video recorder to which cameras are connected and it has a web interface, there is also a raspberry pi with raspbian on board. All this is connected to the Internet via a 4g wifi router from a megaphone, with a dynamic ip. At home, in the city, normal Internet with a white ip. The essence of the question is how to get access from home to raspberry (vnc, ssh). And how to get access to the registrar's webmord first from home, then from wherever you want.
As far as I understand, it is necessary to raise the VPN, if so, then tell me the general scheme of how it should work and some manual for setting it up.

Answer 1

enable ip packet forwarding on the raspberry, install openvpn on the pi and
configure it on the home server like this: debian-help.ru/articles/ustanovka-nastroika-openvp...
on the registrar, specify the raspberry address as the gateway. at home we specify the route to the local network in which raspberry and the registrar are located on the raspberry ip address in vpn

Answer 2

If the registrar is a reputable manufacturer like hikvision, dahua, etc., then they have their own free cloud, p2p is usually called, which does just that. It helps even when it is on a gray network, and there is no way to forward ports.
If this is not the case, then only services such as noip, dyndns remain and figure out the port on the 4g router.