我得讲一篇短文改错,但是我的英语水平很烂,改时写清为什么吧,最好详细点,

我得讲一篇短文改错,但是我的英语水平很烂,改时写清为什么吧,最好详细点,
I have been play piano for four years.Last year when i heard the news which there was going to be a piano performance came up in a few weeks,I felt very nervous.Finally came that day.when we arrived at the concert hall,my hand started shaking expectedly.However,just looking at my teacher's warm face let him get back self-confidence.When it was my turn to perform,I go up the stage and played the piece from beginning to an end pleasantly.Soon,the cheers filled the concert hall.I felt very happy and very proud myself.That is my first piano performance,but I will never forget it for the rest of my life.
一共有十处错误,每句话不超过两处.