If the tank was set up less than 24 hours ago, then I would say the problem you are seeing has something to do with the ammonia levels in that tank.
A new tank has to be cycled - that means a bacteria base must be 'grown' in the filter that will convert toxic ammonia (from fish waste, food decay, etc) into Nitrite, also toxic, and further into Nitrate.
The dimensions you gave suggest a 10 gallon tank. But I'm guessing since there are only two measurements given...
You will have your hands full trying to get that (overstocked) tank cycled with 8 fish in it - and not lose all the fish.
Depending on what the actual size of the tank ends up being, it's probably too small for the Angelfish,
Definitely too small for the Bala/Silver Shark. Those get up to 13 inches (33 cm) long.
If the yellow fish with feelers refers to a Gold Gourami, a very common fish in stores over here, he'll get up to 6 inches and be highly aggressive.
I have no idea what the little insane things are.
Many people lose a lot of fish when they first start out, because they are given horrible information from the store employees. This is good for the store, because you buy more fish... bad for you and worse for the fish.
The best thing you can do is get those fish out of there and return them. Put a couple of Danios or the like in, and let the tank cycle properly. Otherwise, your fish are living in a toxic cesspool - they won't live long.
The main thing you need get right now is a way to test the water. You need to be able to test Ammonia, Nitrite, Nitrate, pH.
The thing you need to do right now is start changing water. Do a 50-75% water change. By the way, if you have chlorinated water, you need to get rid of the chlorine before you can use it in your tank.
