You would use "sort of" when you want to say something went well, but not necessarily as well as you would have liked. A: "Did you do well on the test?" B: "Sort of. The multiple choice was easy, but the essay gave me some trouble." Also it can be used when you want to do something, but you're not absolutely sure. A: "Do you want to go to the park?" B: "Sort of, but I also kind of want to go to the movies." It used in a lot like kind of, actually.