Glad to here Michael has calmed down! I have a mate called Michael - he's a bit highly strung too! 😂
Yeah, your tank looks great for the shrimp, you have a heater in there too so you can regulate temperature (what do you have it set to?), it looks like your filter and its venturi is adding plenty of water movement and DO.
You might want to turn your light down (quite a lot) if it has that function - the high brightness is likely contributing to all the algae you are seeing. If you can't change the light intensity, consider getting some floating plants - I'd suggest either Water Lettuce or Frogbit - they'll help shade the tank a little, and also boost water quality by adding fast growing plant mass.
Also are you dosing a complete plant fertilizer? You're only going to need tiny amounts in a 20 litre tank, but you will need some to help the plants grow and get the upper hand over the algae.
You could probably do with giving it a bit of maintenance - give the filter and heater a clean and get the algae off them, and vacuum up all the dead plant leaves and detritus - in a small tank maintenance is more critical to ensure the best possible water quality, vacuuming is often something you can get away without doing in a large tank with a large shrimp population, but in a very small tank the organics could build up fairly quickly.
Also, is that an anubias on the left side? If so, you want to pull that out of the sand - either just a little to expose the rhizome if the roots have started growing and keep it anchored, or completely and attach it too a little rock or similar if not. Their rhizome should be exposed otherwise it may rot. Don't be afraid to trim the Elodea at the back, and replant the tops and you'll get more growth.
Finally you might want to get some snails - common-a-garden Ramshorns or/or Bladder Snails would be fine (and self sustaining - they will willingly breed in freshwater) unless you want something more exotic. They will help maintain the tank for you and give you an another point of visual interest.