No space before, mandatory space after (if it is not the end of the text). Using space before punctuation is just wrong in Portuguese. This applies for all the cases that you cited: question marks, colons, semicolons and closing quotation marks. Further, it also applies to exclamation marks, periods and closing parenthesis and brackets.
The only exception is that closing parenthesis, brackets and quotation marks immediately followed by another punctuation are not not immediately following spaces, they should be immediately followed by another punctuation.
For opening parenthesis, brackets and quotation marks, there should be no space after them and the space before is mandatory.
So those are correctly punctuated:
Será que esta é uma pergunta simples? Acredito que sim! Pois bem, aqui vamos seguir [mais um] exemplo de um texto (em língua portuguesa, é claro): Tem gente que diz que a língua portuguesa é "simples", mas de fato, "simples" ela não é!
Those are not correctly punctuated:
Será que esta é uma pergunta simples ? Acredito que sim !Pois bem,aqui vamos seguir [ mais um ]exemplo de um texto( em língua portuguesa , é claro ) : Tem gente que diz que a língua portuguesa é " simples" , mas de fato ,"simples "ela não é !
However you are likely to see some very poorly-punctuated text in the internet. The reason is because many people are very lazy and careless when writing in Portuguese. You will also note that very poorly-punctuated texts also frequently features a lot of grotesque grammatical and spelling errors and is poorly-structured, because they are generally written carelessly or in hurry.