After I had had lunch at a village pub,I looked for my bag.这句话中问什么用了两个had呢?各有什么用

题目

After I had had lunch at a village pub,I looked for my bag.这句话中问什么用了两个had呢?各有什么用
还有,当要表达一句话时,什么时候用have,什么时候用be?

答案