Do you have a gravel vacuum? Basically a wide tube attached to a rubber hose that you can use to drain water. Something like a Python water changer (see link below). You can use that to clean out the junk in the substrate and then just stir the substrate up a little if it is the surface of it that has algae on it. You could also just remove the very top of the substrate if you want.
The last picture shows some algae on the glass by the substrate, that is normal. You can push the substrate away and clean it off the glass if you want but it will come back over time.'
You don't want the tank too clean since shrimp feed off the biofilm (bacteria and small algae)
https://www.amazon.com/25-Foot-Python-Aquarium-Maintenance/dp/B000255NXC