Comparison between the first Gantt planning and the last one

Hello, 
I am using Projeqtor for a few months now. I checked on the forum but I can't find what I am looking for. 
I wish I could compare the first Gantt planning when I created my project to the real one. I would like to see for which tasks we were late or if we finished a task before the deadline. 
I always filled in the validated dates. Then the planned dates are calculated according to my ressources. And finally I "fill in" the real dates thanks to the assignations. Until there, everything is fine... BUT once the real dates are filled, I can't see the initial planned dates anymore. The Gantt diagramm shows directly the final / real planning. 
I checked the KPI but I don't manage to have what I want. 
Is there a way to do it ? I would like to be able to make a feedback to my teams about what was planned (or validated) and what was done in reality. 
Thank you for your help.