1.I am growing up while my parents are becoming decrepit .Finally,I know (a thing) that the speed of growing of us can not chase the leaving of parents.
2.as the time I grew up ,my parents have got aged .Finally ,i understand a sentence that the speed of our growing can not chase the leaving of parents.
3..the speed of our growing are not as fast as the leaving of parents.
4.Finally ,my parents are becoming aged ,I understand that after I grew up .
这样吧,凑活看吧,怎么翻译都行,你自己拆了,再拼一个 也行