Hi Fran, welcome to the forum. Whereabout do you live?
To answer your questions about discus :
Discus can live in either hard or soft water and at any PH provided that they are stable and not fluctuating all the time.
Discus can be kept with a variety of other fishes eg. cardinal tetra, rummy nose, small plecos, cory, otto... Basically most fishes that are not aggresive and can tolerate a higher temp (28-31). hth
To breed discus you will need soft water and for growing up babies you will need hard water for better growth. Babies will still grow in soft water but not as well.
Cheers,
ron