The minimum size for a betta is 5 American gallons or 20 litres, though some people think half that is OK.
I can't tell what size your tank is from the photo, but if it is too small for a betta, it is far too small for zebra danios. Despite their small size they are such active swimmers that they need a tank that is at least 3 feet/90 cm long.
But to help you choose fish, can you tell us the hardness of your tap water, please. That information should be somewhere on your water provider's website. We need the number and the units as they could use any one of half a dozen different units.
You need a heater as soon as possible as cycling goes faster in warmer water.
Are you adding ammonia to cycle the tank? If not, that isn't cycling, it's just running the tank.