I don't know how to write in Portuguese, [I really] don't is an English equivalent of 'não sei escrever em inglês não'. The adverb 'não'means 'not'. The verb 'sei' means '[I] am knowing, do know, know'. The infinitive 'escrever' means 'to write'. The preposition 'em' means 'in'. The masculine noun 'inglês' means 'English'. All together, they're pronounced 'now* seh ee-skruh-veh ehng een-glehzh now'.

*The sound 'now' is similar to the sound in the English adverb 'now'.