In spanish you negate the phrase two times. When you say "No sé nada" you was talking two negations "no" and "nada". If you say "no se alguna cosa = I don't know anything" you are talking about so one especific think that you doesn't know. And, consecuently, if you say "no se nada" you are talking "I don't know nothing" (in general). ;)

In English it isn´t possible to say "nothing", "noone", "nowhere"... in negative sentences. Those words are only used in affirmative sentences because in English we can´t "negate" twice. For example, "I know nothing", "there´s noone at home"... and if you say "I don´t know nothing" it´s grammatically incorrect. That´s why, in negative sentences we use "any-": "I don´t know anything", "there isn´t anyone at home"... However, in Spanish it´s possible. We can say "No sé nada" or "Nada sé" and both are correct. You only have to be carefully with the word order because if it´s before the verb, the sentence has to be affirmative - nada sé / nadie come/ ... - but if it´s after the verb, the sentence has to be negative - no sé nada / no come nadie ... And there´s no difference between "nada sé" or "no sé nada", they´re synonyms.

I don´t know anything = (yo) no sé ninguna cosa / (yo) no sé nada I don't know nothing = (yo) no sé nada (yo) is optional, normally we don't use it you never say "no sé alguna cosa" you can write it: no sé (alguna cosa) but in this case is like a blank space no sé ________ Greetings

Usually in spanish is very common, specially in Latin America, the use of two negative phrases in the same sentece, when you say "No sé nada" you try to say that you knowledge is poor or you ignore something, but literaly isn't correct you may say "Nada sé" or simpy "No sé".

Yeah! I know how to use in English but when changing to Spanish, kinda harsh for me!!! Coz I have to add 2 negative words in same sentence while in English, you'll have to use one as you said!!! Yeah, I will learn step by step as you said!!! Thanks