the is a definite article so it is a used in so many things just like ordinal numbers noun and its kinds and river lakes oceans mountains and holy books newspapers and wall no buildings and some countries so the word is very important

just remember the could is used to talk about something that can happen would is used to talk about something that will happen in an imagine situation and should is used to talk about something that ought to happen or must happen

yes it is a correct sentence

every language is hard