"The girl drinks milk."
Translation:La fille boit du lait.
how does the "du" work in this, I dont understand why its needed if "boit" means "drinks" but "du" makes it plural, is that not redundant?
The 'du' is not redundant in this sentence. It roughly translates here as 'some', e.g. "The girl drinks some milk". It is often left out in English but it is important in French. It doesn't make anything plural.
linguistically there is a difference between: The girl drinks some milk. ( this scenario give us quantify, possibly she does not like milk a lot but does drink some from time to time) and The girl drinks milk. (this is a general assumption, something that she likes and does, She drinks milk. no quantity involved.