Is it normal that my tongue has a slit in the middle?

Depends: The answer depends on the history and whether there is ulceration or not.. If it just a anatomic variety, then no big concern. If it is a cut opening and is with apparently unhealed inflammation, then it is not a normal situation and need medical attention.

Yes: It is called a fissure, and fissures in the tongue are quite normal. See the diagram.

Tongues can: Have morphological differences in appearance / shape. Best to be evaluated by your dentist, but i would guess you're fine. Hope this helps.

Tongue anatomy: Having a midline slit or fissure from the back of your tongue to the front is quite common and may or may not be present and to different degrees. If you have any concerns, see your dentist just to be sure.