帮我看看下面的作文有什么语法方面的错误并纠正,如果20分的作文这篇可以给多少分?
I just came back Beijing last week.It is a very beautiful city that I visited it on July22th to July26th with 15 students from different school.We visited many places of interest ,such as the GreatWall,the Palace Museum,the Summer Palace and several famous university.My favorite place is Peking University which it is my dream school so that I encourage me to study hard.The best thing that I made very new friends of that travel.But because of the hot weather,I felt uncomfortable.What a pity!But in a word that the travel was full of interesting.