j'en suis sur

please explain J'en what does it mean?

The answer to this involves grammar that will be covered at a more advanced level, but basically 'en' is an indirect object pronoun that is used to convey an inanimate "it" that is preceded by "de". The lesson on "Y en En" appears in Level 3. So, if you have a sentence like: Je suis sûr de cette histoire. [I am sure of this story.] To say, "I am sure of it" is: "J'en suis sûr." [where 'en' (it) refers to "cette histoire"] Also, the *Je* is contracted to *J'* because the succeeding word, *en*, begins with a vowel. I think at this point in your RF French studies (since this phrase is used in 2.1), it's better to just get a sense of the language, get a feel for how sentences are constructed and learn some phrases instead of trying to decipher all the complex grammar rules all at once because, without a good grasp of how the sentences are structured in French in general, it's a challenge to answer these very broad grammar questions.

excellent explanation merci