É uma boa pergunta.

Inversion is required following negative or certain limiting adverbs, and expressions beginning with “not”. I’d recommend you simply memorize the most common ones (your course-book should have a list in the relevant unit). This is typical of formal style; rarely will you hear this in conversations with your friends ;) Should you want to avoid inversion, simply start the sentence with the subject instead of the negative adverb. So, your correct sentence is the second one — with inversion. Cambridge saves me the trouble of writing more details: