Mollies can be finicky. Wouldn't be my choice for a beginner.
But one doesn't really breed livebearers. It takes some dedication stopping them doing so.
The trick is to catch the babies. You do this by observing your fish, you will eventually be able to tell almost exactly when they will have babies.
Then move the mother to the birth tank with lots of rocks and things babies can hide under while they get used to being alive. This tank should also have lots of floating cover. either plants (more messy) or things like upturned plastic spawning grass patches. You can scrunch a bunch of net together on one side of the tank, with holes too small for the females to go after fry.
Another thing is, if you keep them with other fish, you will loose more fry/eggs.
Your danios are probably laying eggs every morning at daybreak.
All you need to do is put them in a tank with a large net draped in the bottom, so they can't reach the floor, cover it with and inch or two water, chuck some moss or a clump of spawning grass in the centre, the love being able to tunnel under or climb on top of the plant target. Their eggs are not sticky and will fall to the floor, by 10 or 11 the breeding should be over and you can take the net containing the adult fish out again, so they don't poop on their eggs. and you don't have to feed in there exposing the eggs to rotting food particles. Put a little methylene blue in the water and stir well. After a day or so you can use a sterile eye dropper or turkey baster to suck up spoiled eggs and faeces. This all sounds easy and exciting and it is, but it pales against the despair of not being able to care for the fry. There will be many of them, they want to eat the whole time, a fry without a swollen belly is an unlucky fry.
This leads to picking on each other etc. So malnutrition is not just a developmental issue. If you have a green pond or swimming pool (or maybe a neighbour who doesn't mind you skimming a bucket full off once in a while), the first part of the raising fish thing is easy. The food will be everywhere around them, and they need to spend no time trying to find bites to eat, or figuring out that the human says it is meal time now. Otherwise you need to start a culture of baby brine shrimp which can take 3 days for the first to hatch, or get hold of some micro worm culture (stinky). A commercial option I have used with limited success is Liquifry no1, it is basically a precursor to little water critters and yeasts that the little fish can live off.