Extending background with Objects in the way

Hi,

The Clone stamp could remove the background quite swiftly. Here is a good Tutorial: https://www.youtube.com/watch?v=956GC_w-Idg

Sim

For the area not near her arm, you might even want to duplicate the background to a new layer (select some of the wall with the rectangular select tool, and Cmd (Ctrl)+J or Layer>New>New Layer Via Copy. Then, on that layer, use the Transform>Warp on those pixels.

For the arm area, Clone absolutely would work. You just have to ensure you're not trying to clone from the pixels directly next to the area you need. When you Option (Alt) click to get your sample pixels, choose from the area above that has no arm.

You may also want to do that on a new layer (and on the Clone Tool, tell it to Sample All Layers in the Options bar). Cloning takes practice, but if you do it slowly and consistently check and adjust your sampling area, you can do some magic with that tool.