I am self-studying French using the Contacts book by Valette.
I came across the following expressions: avoir de bons amis and faire de grands progrès. I am confused why the book uses "de" in both cases since the noun that follows is plural.
Shouldn't it be avoir des bons amis (with des being the plural of un/une) and faire des grands progrès (with des being the partitive article)?
I would appreciate some clarifications. Thanks!