Complex sentence: The Doctor joins the wedding festivities; afterwards, he returns River's diary and the vortex manipulator to her so she can return to her own time; she sadly tells him he will soon learn who she truly is, and that it will change everything.
Split into simpler sentences: The Doctor joins the wedding festivities and afterwards, he returns River's diary and the vortex manipulator to her so she can return to her own time. She sadly tells him he will soon learn who she truly is and that it will change everything.