More than 25 years after the formation of ultracold molecules at Laboratoire Aimé Cotton (LAC) in Orsay, the first molecular Bose-Einstein condensate (BEC) was created this year in 2024 in the USA. To achieve this, the experimental team used a microwave shielding technique between two molecules, technique that we proposed and investigated back in 2018 during a previous Master 2 internship. As in atomic BECs (see the 2001 Nobel Prize in Physics), collisions between three particles are also important to understand. This Master 2 internship will consist of theoretical and numerical investigations on three-body interactions of the molecules in the presence of the microwave. We will determine the conditions under which three-body protection can be efficient.