Importing CSV to Modify Existing Tasks

When I try to import a CSV file to modify the progress of an existing task in Gantt Project, it creates a new task with the same characteristics but a different progress percentage instead of modifying the existing one. I don’t understand what the problem is or if it’s actually not possible to do what I’m trying to do. Please, I need help from someone who knows about this!

It works as designed. Import is import, it creates new tasks.

Okay, so I need to know if it is possible to import only certain data (from Excel or CSV) into an already existing task. In this case, I need to import the progress percentage into tasks that already exist in the project Gantt chart. Thanks, regards!

I do not import it. I do manually, and frequently, to check whole progress and baselines.

It is not possible, sorry.