Ammonia at 3 (as noted in your log) is high. Daily, and I mean every day, partial water changes of half the tank volume, using a good water conditioner, will hopefully save the fish.
What water conditioner are you using? One that detoxifies ammonia and nitrite would help, Prime does this, also one called Ultimate made by Aquarium Solutions. Either would be beneficial in new tanks.
Your pH is shown as 7; which test kit are you using? I may have more on this.
In a new tank without many live plants I would also highly recommend a biological supplement that helps to start the bacteria sooner. There are two I know of that are worth using, Tetra's SafeStart and Seachem's Stability. A small bottle of either would help. They do not "cycle" a tank, they merely add the necessary live bacteria to get it started faster with less stress on the fish. And ammonia and nitrite are highly toxic to fish.
Lupin is absolutely correct, in a small tank fish choices are very limited, but we can talk about possible fish later, let's get the tank cycled and save the fish you have first
And, welcome to Tropical Fish Keeping forum.