Definitely read the links about tank cycling and Google the nitrogen cycle on YouTube. I recommend checking out videos by kgtropicals and/ or aquarium co-op on the nitrogen cycle, both channels have great videos explaining it. Kgtropicals has great videos aimed at new fish keepers in general.
I just wanted to add about the ADF
... It really helps to spot feed them. In a tank with so many other fish your African dwarf frog probably isn't getting much of any food.
What are you feeding the ADF
I know they sell pellets for them but in my experience I've never had an ADF
that would eat the pellets. They really like frozen bloodworms. Stop taking your frog out of the tank to feed it and get a pair of aquarium tweezers to spot feed him. You can also feed Frozen brine shrimp with a turkey baster.
One other thing I want to point out...I might be wrong...but your tank sounds like it has a lot of fish in it and it might be overstocked. I would go to Aqua advisor and input your tank size and filtration and see if you are overstocked or not.
Good luck and keep us posted on how things work out