return作"归还"讲时,后面是不能加back的
常用于固定搭配:return sth to somebody “把某物归还给某人”
如:I return the book to him. 我把书归还给了他
后面加back时,作“返回”讲,常用于 return back to... “回到...,返回到...”
如: I suggest you return back to your vehicle. 我建议你返回到您的车辆。
I want to return back to china firstly, give money to my parents and relatives.
首先,我会立刻返回中国,把钱分给我的家人和亲戚们。