This is the most used name for this fruit across the world, including its scientific name.
In English, the verb changes from plural to singular depending on the number of people performing the action. So you have "They eat", and "He/she eats".
In Portuguese, the forms of the verb differ similarly- So you have "A mosca come um abacaxi" (The fly eats a pineapple), and "As moscas comem um abacaxi" (The flies eat a pineapple).
In English, singular users get the plural forms of the verbs (He eats/walks/sleeps), and plural users get the singular forms of the verbs (They eat/walk/sleep)
In Portuguese, singular users get the singular form of the verb (Ele come/caminha/dorme), and plural users get the plural forms of the verbs (Eles comem/caminham/dormem)
This is not correct. The "s" in "he eats" is not an indication of plurality, as much as the "s" in "tu comes" is not either. Verbs usually change (conjugate) in a completely different way compared to nouns/adjectives/pronouns. In English present simple tense the usual pattern is very simple. Third person singular verbs end in -s. All other forms are the same as the infinitive:
I/you/we/they eat (note that "I" is singular, but takes the same form as the plurals)
It would, but we're not making sense of the sentence... We're translating it. I don't disagree with you, and making sense would greatly help the learning process, but it's like "dois mais dois é cinco". The correct translation is "two plus two is five", but that obviously doesn't make sense, you know? Even in Portuguese it doesn't make sense lol, but that's what the translation is.