Questions & Answers about O aluno não abre a porta.
Since abrir is an -ir verb, why does it end in -e (abre) instead of -i?
For regular -ir verbs in the present tense, the third-person singular form (used for he, she, and you formal) takes an -e ending. To conjugate it for O aluno (which counts as "he"), you drop the -ir from abrir and add -e, making it abre.
Why is there no Portuguese word for "does" in this sentence?
Does aluno mean this is specifically a male student?
Yes, aluno is a masculine noun, so it refers to a male student (or a general student when the gender isn't known). If you were talking about a female student, you would change both the "the" and the noun to be feminine: A aluna não abre a porta.
Is the "e" at the end of abre silent?
It is not completely silent, but in European Portuguese, an unaccented e at the end of a word is pronounced very briefly and softly. It sounds more like a quick "ih" or a swallowed vowel, rather than a strong "eh" sound.