It doesn't sound normal. "worse-" doesn't fit as a replacement for the "im-" prefix, because the "se" ending doesn't flow well into the plosive "prov".

"disimprove" works much better.

The similar word "unimproved" implies you did nothing to make it better, "disimproved" implies you actively made it worse.

But this is still just effectively adding "not" to the word. If you must join two words that are the antonyms of each other (like verbessern and verschlimmern), the closest match I can think of is the vulgar pun "fuxed", a blend of "fixed" (repaired) and "fucked" (broke). https://www.urbandictionary.com/define.php?term=Fuxed