As mentioned above by Tony, Elmer's drawings are an excellent place to begin and are proven designs. Steam engines have been around and improved on for around 200 years so you may not need to redesign it. However if you still want one all your own, study all of Elmer's drawings and choose a style to develop. You might also look into Rudy Kouhoupt's designs as they are also excellent. (I hope I spelled his name right)
From what I can see your English is excellent.