For an area of that size, the best solution by far is to buy roll-out sods. Many websites give complex advice on it, but for a small area, much of this is unnecessary. You can lay them now - and apart from removing surface weeds and making sure that the surface is level the work involved is minimal. Use a carving knife to cut to size, and then press it in with your shoes/boots and water it if it is dry. Very few weeds, if any, will ever penetrate, and you will have a beautiful lawn immediately. There are a number of grades available from the better suppliers, but the cost for this area should be well below €50 if you collect and lay them yourself.