It is difficult and it will take a lot of time. But, it can be done if you want to get it done. Just start with something simple, either a simple VN with 1-2 branches or try to break your game idea in different components and learn how to make those. For example, start by programming the Harem part of it ( interactions with the characters, how to display different scenes based on some conditions) or start on the quest system. This way you will have a set objective and if you finnish that, you can start on the next one. In a couple of months, your game code will be done. Then all you need is to find the artist/ images.