Argumentative and proving skills are considered key competencies in mathematics. Collaborative learning activities, by fostering students' production of conjectures and arguments, could contribute strongly to the development of these skills. In this paper, we present the design of a e-learning collaborative environment, whose goal is to promote in students the move from arguments expressed in colloquial registers to arguments expressed in literate registers, i.e., the move from argumentation to proof. We also describe an example of implementation of such an environment by integrating GeoGebra within Microsoft Teams. The result of this integration is a stimulating and user-friendly environment, which overcomes some of the limitations related to the graphical aspect that characterize many online and e-learning platforms. In the future, we aim to test this environment on a large scale, with many students and teachers, to verify its effectiveness both from a mathematics education point of view and from a user acceptability point of view of the graphical interface.