Did you grasp the overall situation?你懂我说的意思吗

"今天的几个句子是有关征求意见的：1.It's a great deal. 这可是笔大买卖。2.Do you happen to know...?说不定你知道……吧？I can't tell the difference.我辨别不出来。3.Do you know what I mean? 你懂我说的意思吗？4.You have to improve. Understood? 你得有所提高，明白吗？"