'não' means 'no/not/don't/doesn't' , in portuguese there's no auxiliar verb for negative sentences , so we use always the same word 'não' 

Ele não gosta de sorvete (He doesn't like icecream)

Ela não é professora (She's not a teacher)

Não! Não faça isso! (No! Don't do this) 

Actually, it's common to hear people pronouncing 'não'(naang-oo) as 'num'(noong) when it's before a verb (it's informal way) 

Ela num é professora (She's not a teacher)

'Não' and 'num' are correct in speaking, although we write always 'não'(formal way)

'num' is only used in informal speaking and in some dialects there's no difference between these words) i hope u got it!  

First notebook entry: Introducing myself

Eu nao falem portugues lol

Eu não falo português.