Hi Lukasz,
The Exam Content Outline only mentions that experience must include leading and directing projects, it does not mention a requirement for projects to be closed. When I applied, I included some projects still ongoing for my experience. The important thing for your application and what counts towards the experience is that you are leading the project, so make sure you use key words taken from the ECO when describing your experience as PMI will be looking for those key words. Other than that, good luck with your application!
Regards,