If my dag fails for some reason, is it possible to re run the dag without loosing the progress?

Airflow dag is a collection of tasks, organized in a way that reflects their relationships and dependencies. So if you have a dag with 3 tasks: A -> B -> C, when the task C fails, you can just re run it without re running A and B, But if you re run the dag, that means you re run the task A with all the downstream tasks (B and C).

If you want to restore the progress within a task, you can do that based on your job logic but this is not related to airflow, it depends only on the techno you use and the logic you want to implement. For example, for your data, if you have multiple files in the dataset, you can create a state store on cloud storage or a database, to know the processing state for each file, and if the file is already processed, you can skip the processing and pass to the next one.