The 1st thing to do is to try and enable port forwarding in your router assuming that this is possible. You have to to check first if the port(s) is open again using https://canyouseeme.org while keeping the below notes if it didn’t work:
1. You did not configure the router properly to allow for port forwarding, so please make sure that you do some research of your router model, cause every router model has a slightly different method to enable port forwarding.
2. The port is not actually open in Kali, so make sure that the service is actually running in Kali on the required port.
3. Your ISP (Internet Service Provider) does not allow you to forward ports, so please call them to check/
As for the above method using intermediate servers, as mentioned above, it won’t be covered in any course, but you can set up your own server for the procedure, and search online if you can find anything related to this subject, but I can’t guarantee one way of doing this, so it’s best if you do further research on this… I hope this clarifies better.