I have had lunch.怎么变成过去完成时

I have had lunch.怎么变成过去完成时 I've already had lunch过去完成时,这句短语中请问怎么运用理解啊? I have already had lunch 是什么结构 I have had lunch at school 对have had提问 i have alreay had my lunch 【】you [ ]your lunch [ 英语翻译如 I have already had lunch.l have just had lunch.那l have i have had enough 这算什么句?过去完成时? I have had lunch为什么用两个have? 过去完成时.I have got a cold.对还是I had got a cold对?这些应该怎么用? I've already had lunch.Have you had lunch yet?这是什么时态呢? I have had lunch at school.对at school提问 I have had lunch at home 改否定句