Adding more backdrop to pictures PLEASE HELP!!!!!!

In PHOTOSHOP- You would do something like this-

1) Select the blank area of the background (Quick Selection Tool?)

2) Go Menu > Edit > Content aware Fill

3) Use the brush to erase any green overlay (Sampling Area) that covers the faces. The overlay should only be on the wanted background to use for the 'Fill'.

4) Apply

And if you extend the 'Canvas' (by Crop tool) you can also 'Content Aware Fill' more of the background above the heads.

I'm not a master at using those Photoshop tools. I've watched some master classes on how to use them, and those who really know how to do it can work wonders. I don't know what you used or how you implemented the techniques. All I can suggest is to keep trying. I'm curious as to why you asked this question in the Lightroom ecosystem forum if you used Photoshop to try to make the changes.

If what you mean is that you want to extend the backdrop, I think you need to use Photoshop rather than Lightroom. There are some tools in Photoshop that would make it easier to accomplish the task. Lightroom is a nondestructive editor, so what you are wanting to do is a little heavy-handed for Lightroom alone.