"some" has various translations according to the meaning of the sentence:
I buy (some) coffee and (some) beer = j'achète du café et de la bière = partitive case, with an uncountable and singular noun. In this case, "some" means "an undefined quantity of a mass"
I buy (some) bananas = j'achète des bananes = plural of I buy a/one banana = j'achète une banane. In this case, "some" means "an undefined number of"
some bananas are rotten in this basket = certaines/plusieurs/quelques bananes sont pourries dans ce panier. In this case, "some" means "a certain number of" (close to "a few/several" = quelques/plusieurs)
"des" is the plural indefinite article that English does not have:
- une robe = a/one dress
- des robes = (some) dresses
"du", "de la" and "de l' " are partitive articles to translate "some" (as a word or as a meaning) in front of an uncountable noun:
- je mange du pain (masculine) = I eat (some) bread
- je bois de la bière (feminine) = I drink (some) beer
- j'ai de l'argent (masculine, starting with a vowel sound) = I have (some) money
- je veux de l'eau (feminine, starting with a vowel sound) = I want (some) water
If the English sentence has "the", don't even think and translate with le, la or les.
If the English sentences has a bare plural noun, like here "dresses":
- if you can add "some" in front of the noun, the French will be "des" (plural of un/une)
- if you can add "in general" after the noun, the French will be "les" (generality)
"Des" is the plural indefinite article that English does not have.
"Des" is the plural of "un" or "une" and it means "more than one": singular "une robe"; plural "des robes".
"Des" is replaced with "de" before an adjective: singular "une belle robe"; plural "de belles robes"