Adding a sprint after the fact

[Jarl_Andreassen]

Hello community.

We are a team of 6 students working with agile scrum.

We have used the collaboration tool Monday until now, but realised there were no burndown-chart capabilities there. We were recommended Jira and are trying to transition to Jira now.

We tried importing the sprint board from Monday by CSV to Jira, but without success. Too tideous and complicated honestly.

We decided it wouldnt be too much work to import it manually by adding each Pulse from each sprint after the fact. There are 70 pulses who needs to be moved.

I've now tried to manually insert the different pulses into their respective sprints on Jira, Starting the sprint and then added each pulse to "Done", finishing the sprint after the fact.

Even though i added start and end date to each task as well as time estimate and time spent, when i requestet the burndown chart for the sprint it came out showing all tasks started and ended on the same day. Im super confused over this.

Does anyone know how to add a sprint and complete it after the fact? Is it possible?

Sorry in advance for my probably cluttered description of the issue. Please ask if you dont understand. 

Regards