Which sentence is grammaticaly correct?

We could manage to repair only one unit and other one is beyond repair, but there will be a charges for inspection. This unit will work only for 3 minutes. It will stop working every 3 minutes.

One unit has been repaired and it is in working condition. other unit is beyond repair, but there will be a charges for inspection. This unit will work only for 3 minutes. It will stop working every 3 minutes.