The GeoGebra Workshop for the degree "Teacher in Primary Education" has been designed to work the main geometric competencies that primary pre-service teachers need to develop. In this paper, some case studies are included in which we analyse the development of geometric skills and the use of GeoGebra dynamic tools in three types of activities: reproduction of constructions, properties verification, and conjecture and research. We find that the "dynamic" nature of GeoGebra is not used by students from the beginning due to their previous static learning experiences. Another difficulty with some of the students is the geometric language comprehension. Dynamic software like GeoGebra can help to overcome these problems. After analysing a survey filled out by students at a GeoGebra workshop, 80% of the pre-service teachers believe that this software can help them to improve their geometric knowledge and that it will be a useful tool in their future work as teachers. (Contains 7 figures.)