首先一个问题是你的逗号,逗号前面没有空格,后面有空格。第五句改成A course of instruction is necessary to swim properly更顺畅。第六句逗号用错了。一句好里面两个逗号这样放着就代表你去掉逗号里面的句子整句话也会通,但是你这里不通,所以应该是Returning home after work, supper was waiting for him in the kitchen.第七句要加个a, the young man is honest and hard-working, also a very reliable worker.第八句改成There are many ways we can use to get to know the outside world.