First of all, please understand that the optional projects are not the central focus of the program. Your own research project comes first at all time. If there is an overlap between your research and the focus of one of the projects you can of course find a ground for collaboration.
Each optional project will present some activities in which you are welcome to participate, but this is not mandatory. It simply provides the opportunity to along with a researcher in his/her/their field, gain deeper knowledge and get inspired.
If you are specifically interested in one of these projects it is mandatory to contact the leading researcher beforehand. This can only be done through this online form