The difference between 'I don't know nothing else' and 'I know nothing else' [duplicate]

Solution 1:

Standard Englishes (all of them) do not allow so-called "double negatives" like your first example, which is ungrammatical in them.

Many speakers throughout the Anglosphere use forms like your first example in their ordinary speech: in their non-standard varieties of English, the form is grammatical, and has the same meaning.

All English speakers understand the first (to mean the second) unless they are being deliberately perverse; but many never use such forms.

I advise a learner never to use the first form unless you understand the social implications of using such a variety of English; but expect to hear and understand it.