Hi and welcome to the forum
What are the tank dimensions (length x width x height)?
What is the GH (general hardness) and pH of your water supply?
This information can usually be found on your water supply company's website or by telephoning them. If they can't help then take a glass full of tap water to the local pet shop and ask them to test the GH & pH for you. Write the results down (in numbers) when they do the test, and ask them what the results are in (eg: ppm or dGH).
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Livebearers (mollies, platies, swordtails, guppies) naturally occur in water with a GH above 200ppm (250ppm for mollies) and a pH above 7.0. If your water is too soft (lacking minerals) and has a GH below 200ppm or pH below 7.0, the fish won't do that well.
The other fishes you listed all come from soft water with a GH below 150ppm and a pH below 7.0.
If you want to keep livebearers, then keep them in a separate tank where you can give them hard water, and keep the other fishes in soft water.
Livebearers naturally occur in large groups of females with 1 or 2 males hanging around the group trying to breed with them. In an aquarium I recommend keeping all males or all females so the males don't pester and harass the females.
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Try not to buy dwarf gouramis (Trichogaster lalius) or any of their colour forms because they can carry two nasty diseases, the Iridovirus and Tuberculosis (TB), neither of which can be treated and once the diseases are in your tank, they are there until you scrap the tank and disinfect everything with bleach.
If you can get locally bred dwarf gouramis they are usually fine, but anything that is imported from Asia could have either or both of these diseases.