Looking for idiom meaning "to make many serious or stupid mistakes"

I'd suggest "make a hash of", which is defined by oxforddictionaries.com as "make a mess of; bungle".

This phrase seems especially apt as a translation of the original Ukranian idiom because the origin of the verb "to hash" is given by the Online Etymology Dictionary as "from French hacher 'chop up' (14c.), from Old French hache 'ax' (see hatchet)".

I think the saying throw the baby out with the bathwater can suggest the idea you want to express:

• to get rid of the good parts as well as the bad parts of something when you are trying to improve it.

  • I don't think we should throw the baby out with the bath water. There are some good features of the present system that I think we should retain. (AHD)

• Though it is right to arrest criminals, if you don't reeducate them it is like throwing out the baby with the bath water.