Hi @bayram, 

Have you had a chance to take a look at this CityGML documentation? It takes you through a basic method of converting to CityGML. Essentially, you’ll want to use the GeometryPropertySetter to define your geometry before writing it out. I’d also recommend taking a look at this template which you can download and plug in your own shapefile. You’ll have to do some attribute management but this template is a great starting point. Let me know if you have any other questions!