Set fixed end dates

Hello, I would like to create a diagram, but as a beginner I am failing a little. I have a submission of my work on a fixed date and a final presentation on another fixed date. Now I would like to set these dates as milestones (so the date should not change) and create the project backwards from there until I reach the start date.

I don’t know if this is the usual procedure, but is it possible to implement this in the current version of Gantt Project? Or is it only possible to start from a fixed start date and changes to individual tasks then affect the end date, not the start date?