Hello
They have told me to end a certain project at a fixed date and calculate everything before that according to that fixed date. I went into the last task and tried to do "finish no later than" but it didnt have any effect.

how can i calculate everything on a schedule based on a fixed end date that must not change? they want to see when they should start the project. i know that by iteration of the initial date to various dates i can also do this but i want to know if there is a better way

On a copy of the schedule, switch specify the Finish date in Project Information.