Learning a new language can expand your horizon. Maybe this one is better.:-)

To open your heart means to be not closed off, in an emotional sense. If you show your feelings, you are opening your heart.

It's fine. "Open your heart" is not a terribly common stock phrase or idiom. Just as "open your mind" means "prepare yourself to receive new ideas," "open your heart" means "prepare yourself to experience new feelings of affection." While I understand the meaning, it seems like an exaggeration to me.

Learning a new language can open your mind and your heart. "...open your heart ..." to someone. ​ To tell someone about your problems and secrets: "She's very understanding - you feel you can really open your heart to her."