为什么外国人听不懂我说的英语?

为什么外国人听不懂我说的英语?
我发现自己的外教老师（英国人）听不懂我说的英语,不是因为我发音问题,而是说话很让对方费解.比如上次跟外教老师在Skype上的对话,
我：Peter 老师：Jack
[20:53:22] Peter::)Jack,How are you
[20:54:15] Jack:I am OK.How are you?
[20:54:40] Peter:Just fine,thanks.
[20:55:18] Jack:Where are you now?At home or still working in the office?
[20:56:58] Peter:At home.I'm waiting for visa in during this time.（表达：这段时间我在等签证办下来）
[20:57:37] Jack:
[20:57:45] Peter:How about you?
[20:58:26] Jack:Visa for your teachers?
[20:58:39] Peter:Yes.
[20:58:53] Jack:I moved from guangzhou to Jiangsu province
[20:59:36] Jack:May I ask about my job application with your school?
[21:00:52] Jack:Were able to hire the teachers you need?
[21:02:20] Peter:Sorry,I don't know.But I think Eddy maybe know.
[21:02:40] Jack:OH
[21:04:43] Peter:Do you has been changed your phone number?
[21:05:18] Jack:My Cell phone# is still the same
[21:05:40] Peter:Ok.
当我跟他说：“这段时间我在家等签证”,为什么他会误解?再比如前几次我在英语角口头跟一个外国人说：“ I'm study in Manchester University at next year." 他听不懂我在说什么,但这句话对同学说,他们都能听懂,这是怎么回事?