I would recommend that you focus on learning the engine, as well as programming before jumping into projects, that way you won’t need to ask how long something will take, you will know based on your experience. Now, obviously working on a project can help with experience, but hopefully you get my point. There is no real way for us to tell you how long anything will take you to make. There have been projects that I thought would have taken a day or two, and ended up taking over 2 weeks, and vice versa.