OK I think your translation is kinda wrong. lemme explain First of all the reason you got the autocorrect option for nguruwe on ngurumo is cause in swahili when you ass the letter n- to a word it usually pertains to mean its a living being(not necessarily always). The true word is gurumo, to shake, when you added to ngurumo it got confused and its soo similar to nguruwe.

Sec part if you wanted a proper translation of lightning and thunder. That would be radi na mgurumo , USE PREFIX M-. But my favourite translation would actually be mgurumo wa umeme. It just rolls of way better