‎Mt skinner is my favorite mountain! I love hiking there I took the picture at the Grand Canyon 聼起來自然嗎?

If the listener is looking at the picture from the grand canyon, or if they know which picture you are referring to, "the picture" is correct.

If they have not seen the picture, and this is your first time talking about it, use "a" instead.

Also, I'm not sure if you meant "Mt. skinner"? I don't understand "My skinner"