“And these are just some of the reasons why you should learn a new language” (or just “you should learn a new language”).
Thesis statements are like a broad overview of the point the writer makes in their writing. The writer provides a lot of specific information about the benefits language learning has, but they end the paragraph with the broader statement, “and these are just some of the reasons why you should learn a new language”. Because this sentence is broader and gives an overview of what the author wrote about in the paragraph, we can infer that that sentence is the thesis statement.
