I want to use two B-L072Z-LRWAN, one as an end node and the other as a gateway. I am all set with the end node but is it possible to set B-L072Z-LRWAN as a gateway between the server and the end node.

[Tesla DeLorean]

The radio can receive the signals, you'd have to own the task ​of writing the gateway functionality.

It is not well suited to dealing with multiple nodes transmitting at random times, and on top of each other.​

[Tesla DeLorean]

A pair of B-L072Z-LRWAN can be used in a point-to-point mode, more could broadcast one-to-many.

For a gateway class device look at https://www.st.com/en/evaluation-tools/p-nucleo-lrwan3.html

[SSing.3]

Can I have two  B-L072Z-LRWAN talking to each other?

[Tesla DeLorean]

Yes, like I said point-to-point

The ping-pong example alternates, but you could just as easily have a committed transmitter, and a committed receiver, and send GPS coordinates and temperature measurements, for example