First you have to setup the 4G dongle to connect to your provider and this way you can get into the internet. You should be able to
ping google.com from the RasPi. We cannot help you much with setting up the dongle because it is a specific device and not belonging to Raspberry Pi. If you have done it then you must have an interface representing the internet connection, maybe
Bridging this interface with
eth0 is not advisable for this simple task. Over the internet you can only do it using a virtual private network (VPN) with a
tap interface. It is overkill and not worth the effort. So you should just use routing with different subnets for the laptop and for the sensor.
The next problem is that the laptop connects through the web to the 4G dongle and it only sees the public ip address given from the provider of the dongle. This public ip address may be change from time to time usually when you establish a new connection with the RasPi. You can use a dynDNS service so you can use the same DNS name for the changing public ip address. dynDNS will always assign the right ip address to the DNS name. Or you can purchase a static public ip address from your provider.
Another problem is that the 4G dongle (and any other router) uses network address translation (NAT) to connect to the internet. This is the method to translate private ip addresses, e.g. 192.168.0.0/16 to the one public ip address seen from the internet side. So you have to use so called port forwarding to find the way backwards from the one public ip address to your sensor. Maybe it isn't needed with this one to one connection but I don't know it now without details of the configuration. If needed it must be able to configure the dongle with port forwarding.
You wrote in a comment that you already have access to a Graphical User Interface (GUI) on the RasPi via internet with VNC from the laptop. I assume you have MS Window$ running on the laptop and need to run a program that accesses the sensor by its ip address and on a specific port. This means we have a server running on the sensor serving data to the specific port. We have a TCP connection (ip address and port) that can be routed/redirected/forwarded/bridged/whatever like any other TCP connection.
With a ssh tunnel it is possible to access the port on the remote sensor with port redirection. On a laptop with a Linux operating system it would look something like this, if you want for example to access a secured web server:
laptop ~$ ssh -nNT -L 4433:10.0.0.126:443 public-ip.raspi.dyndns.com &
# In a web browser use this URL
laptop ~$ https://localhost:4433
This will redirect access to port 4433 on the Linux laptop to port 443 on the sensor (10.0.0.126). I don't know how to do it on MS Windows. I know it's possible but out of scope here.
I suggest to setup it in two steps. First build a SSH tunnel. You should establish a Secure SHell so you can login on your remote RasPi. As far as I can see, the tool you are using, can do it. Just select "1) SSH on port 22" instead of "3) VNC on port 5900". You should be able to login to the remote RasPi to a shell with command line. If this is working then it should be no problem to make the SSH tunnel.
Second: setup port redirection. To reduce possible error sources you should do it first on your local network. You already have a direct connection to the sensor as shown at your other question How to connect a ethernet device wirelessly by my laptop?. If you can access the local sensor with the monitoring tool using the ip address 127.0.0.1 or localhost and the port you have specified, then you can make the ssh tunnel and redirect to the remote sensor.