Help please, how do you say "Jane thinks you are interesting" in French?

Jane pense que tu (vous) es (êtes) intéressant (s).

Use "tu" if you are non formal with the person.

Use vous if you are formal with the person.

Use the -s of plural if you are talking to several people.

Assuming the person Jane finds interesting, is a male:

Jane pense que tu es intéressant --> Jane thinks you're interesting

Jane croit que tu es intéressant --> Jane believes you're interesting

Jane te trouve intéressant --> Jane finds you interesting

Selon Jane, tu es intéressant --> According to Jane, you're interesting

You can use any of the above sentences. Please note that if the person Jane finds interesting is a female, you need to add an "e" to "intéressant" .. so you end up with "intéressante."