Do you mean the Magic Wand tool? The magic wand is used to select areas where the color is similar, or if you're lucky/good, you can get it to select an entire object in an image. It's not meant to select all.
If you want to select an entire layer, use CTRL+A, or Edt > Select All. This will make the selection cover the entire canvas and it'll stay active until you deselect it, no matter which layer you want to work with.
If after you've pasted something and you want to remove the selection from around what was pasted, use CTRL+D, or Edit > Deselect.
If you want to select just a portion of something, use the Lasso tool, or the Rectangle or Ellipse Select tools.
And if you want to the image to be just one layer instead of several, go to Image > Flatten and it will flatten all layers into one.
If none of that answers your question(s), maybe tell us more what you're looking for. I'm not using Team Viewer.