Four lessons really isn't that many. It can take time to build up the spatial skills and muscle memory you need for driving, and the only way to do that is through practice. Don't expect too much of yourself at this stage, and when you're out in the car, try not to overthink things. I found that I got much better when I was more relaxed and not trying to rehearse every step of every manoeuvre in my mind before I did it. Again, this is something that comes with time and practice. Another thing that helped me was variety in my lessons. When I was having trouble with roundabouts my instructor would never let me spend the whole lesson on them, because that way it just gets harder and harder to focus. You need to be practising a mix of skills.