28 litres is a bit small for a dwarf gourami, I'm afraid. And the ones bred in far east fish farms are likely to already be infected with an incurable disease. I have a 23 litre tank (a 30 cm cube) and I've had rectangular 25-ish litre tanks in the past so I know how small your tank is for finding fish that'll be suitable. My 23 litre is currently a shrimp tank.
Endlers and shrimps, yes. I've kept endlers with red cherry shrimps, though in a tank with a lot of decor starting with silk plants then live plants for baby shrimps to hide in. Cherry shrimps come in variety of colours though it's advised to keep all the same colour as different colours will interbreed and you'd likely have all brown shrimps after a few generations.
Since your hardness is not terribly high another option is a betta (also known as Siamese fighting fish). Just the one fish with no tank mates. These are territorial fish which either are so aggressive they attack tank mates or so laid back they are bullied by tank mates. Some will tolerate shrimps, others see them as food. When I kept bettas I had a nerite snail in with them, that's all.
