Tenses 求救!!!

1. He had backed me during the selection process and, more important, knew what he was getting and believed GE needed it. (唔明句野講咩同點解要用was getting?)2. Yet the company, which began with meteoric growth, never sustained its rapid growth after its first three years. (點解見到yet唔係用present perfect?)3. Originally, they had promised to deliver machines within eight weeks, they intended to return to that standard… 4. Having rejected medicine, law and business, Morrie had decided the research world...5. A middle-aged woman came out of her room every day and lay face down on the tile floor, stayed there for hours, as doctors and nurses stepped around her.(點解唔用has stayed 因為我見到個for字 同were stepping)

有colour果d verb 我都唔明點解要用果個tenses 請解釋下