Is this grammatically correct? What does it mean and can it be rephrased? I washed, swept and packed the dung in their pen daily in the course of the training and also weeded the surrounding.

Yes, the sentence is grammatically correct. It describes a series of actions performed daily during a training period: washing, sweeping, packing dung in a pen, and weeding the surrounding area. A rephrased version could be: "During the training, I daily washed, swept, and packed the dung in their pen, as well as weeded the surrounding area."