Learn Portuguese (Portugal): Grande parte das maçãs no pomar estão maduras. - A large part of the apples in the orchard are ripe.

When a singular expression of quantity like grande parte de (a large part of) or a maioria de (the majority of) is followed by a plural noun like as maçãs (the apples), you have a choice. You can make the verb singular to agree with parte, or plural to agree with maçãs. Using the plural verb (estão) is very common in Portuguese because it emphasizes the individual items.

Does the adjective maduras agree with grande parte or maçãs?

It agrees with as maçãs. Because maçãs is a feminine plural noun, the adjective must be maduras. Even if you chose to use the singular verb está in this sentence, the adjective would still be maduras because it is describing the condition of the apples themselves.

I sometimes mix up when to use de versus das. Why is it das maçãs here?

We use das (the contraction of the preposition de + the feminine plural article as) because we are talking about specific apples: the ones in this particular orchard. It literally translates to "of the apples". If we were talking about apples in a generic, non-specific way, we would just use de.

Why do we use the word before ?