make a hash of
Also, make a mess of. Ruin or spoil something, as in They've made a hash of their financial affairs, or She thought he'd make a mess of the garden. The first term, first recorded in 1833, uses hash in the sense of "a jumble of mangled fragments"; the variant, using mess in the sense of "a muddle" or "a state of confusion," was first recorded in 1862.