Hi Udi
Welcome to Wetpixel. We hope you find it enjoyable and useful.
Photographing against - and especially at a downwards angle - the substrate always makes it hard to get the subject to stand out. If you can, and, yeah, not always possible, shoot upwards. And, again, not always possible, look for subjects that stand out against a neutral space or a sympathetic texture or colour which does not overwhelm the subject. A couple of examples are attached of shooting up and neutral backgrounds.
So, if none of the above are feasible, what then? A snoot allows you to light just a small element of the image; using a wider aperture - and therefore less depth of field - will help a little isolate the subject from the background.
Then in post-production. I see you are using LR: the new masks are brilliant for what you want to do. I'd try selecting the subjects, invert and then desaturate and de-clarity the background. Make a second mask of the subjects themselves and tweak a little with Dehaze, Clarity, Texture and maybe White. The key is not to over do it. The best make-up can't be seen! And give Effects > Vignetting a try - maybe at about -11 or -13. That could make quite a difference.