Combine OpenVPN tunnel (to home network) with VPN services like NordVPN/PIA

Hi everyone,

I recently found NovaspiritTechs youtube channel and this cool community which has been really helpful during my latest adventures with the new Raspberry Pi 4.

Recently I installed OpenVPN on my Pi so I can connect to my local home network from a different network, like the library. This allows me to connect to my Samba shares that are also present on my Pi. With this, I can establish a safe connection between my remote devices and my Raspberry Pi. Because I now use OpenVPN on my Windows machine, I cannot longer use my NordVPN services to connect to one of their servers (it just won’t connect). This brings me to my question:

Would it be possible to combine my secure OpenVPN tunnel with a service like NordVPN? Currently, when I connect with my Windows machine, say, from the library to my home network using the OpenVPN server on my pi, my Windows machine gets assigned the public IP address that is assigned to my home network. In other words, my home public IP address is not protected. Does this mean that my Windows machine is not protected when I browse the internet from the library? What traffic is acutally encrypted? Only the traffic from my machine to the Pi or also when I browse the internet? If my internet browsing is not safe how can I change this?

As you could probably guess, I am completely new to the Pi and have only been using it for one week now, so I apologize for any simple/stupid questions! Thanks in advance.