Best practices for fragmentation

I am making an application, and I just started using Fragments, finally, after reading all the documentation, I got here. I developed the application, so in portrait mode, these are two actions, the selector and the details, and in the left left rule - the details on the tablet. Now it works as in this image:

however, now when I turn the phone into an album, it does the same as the tablet in the landscape, it has two fragments. Firstly, I would like to know if I should leave it as two fragments on the phone? Will this be "best practice"? If not, I would like to know how to make a landscape like a portrait without ruining the tablet landscape.

thank