This study looks at how well a new medicine called cagrilintide works together with semaglutide on blood sugar levels in people with type 2 diabetes compared to cagrilintide alone or semaglutide alone. Before a new medicine can be prescribed to people it needs to be tested to see if it is safe and effective. Participants will either get cagrilintide and semaglutide together or cagrilintide and a dummy medicine or semaglutide and a dummy medicine. Which treatment participants get is decided by chance. A dummy medicine (placebo) looks like the study medicine but does not contain any active medicine. The dummy medicine is in the study to see if the study medicine works as expected. Participants will get 2 injections per week on the same day. Participants will take the study medicine with a pen. A pen is a medical tool with a needle used for injections under the skin. The study doctor or staff will show how. The study will last for about 39 weeks. Participants will have 12 visits at the clinic and 5 phone calls with the study doctor. At 6 of the clinic visits participants must not eat and drink for 8 hours before the visit (water is allowed). Women who can become pregnant cannot take part in this study. Only women that are surgically sterilised or post-menopausal are allowed to participate in this study Women cannot take part if pregnant, breast-feeding or plan to get pregnant during the study period