the guests（主语） had,of course（插入语）,realized （谓语）this（宾语） from the moment Bessie opened the door for them（时间状语）,and（连词） long before the final catastrophe（时间状语）,had had （谓语）a difficult time（宾语） trying to conceal their asumement（主语补足语）.
当然,在Bessie开门的时候,客人们就意识到了这一点,而且离最后的灾难很久以前,他们就已经为试着掩饰他们的asumement而痛苦一段时间.
had had a difficult time trying to conceal their amusement
这里是过去完成时态,第一个had 后面要就过去分词,所有第二个have 就变成了had,所有就有两个had ,这里had a difficult time 的原形是have a difficult time ,是指很难怎么样