COMMENT： I can get what you mean when you say“我学校” , but "我校"or “我们学校” will be better. "我校" is formal than "我们学校"。and ummm, in Chinese you will need a measure word between the number and the noun. It's quite annoying sometimes:( so here, 一百名留学生的....，or 一百封留学申请书
COMMENT: “地上的天堂” is not wrong, but personlly “人间的天堂”will be better
COMMENT: here "可以" is not necessary, because 可谓 actually means "可以被称作", you can regard it as a verb.
COMMENT: this word 源远流长 will usually not be used in a negative situation. that means you can not say the war is 源远流长，instead, you can say like, the history or the culture is 源远流长。
ADVICE: 因为这两个国家间战争不断，所以它们如今的关系不太好。 /中国文化源远流长，我们要继续传承下去。
COMMENT: this setence is a bit strange.I don't get the logic here:( “出气”means vent one's spleen or anger. I guess it has nothing to do with "书写" right? 书写can be used as a verb or a noun.
ADVICE: 他的书写很潦草。 this word is used as a noun here. meaning: your writing is poor.
书写汉字并不难。 here used as a verb, it means: it's not hard to write chinese
他喜欢用写作来出气。He likes to vent his anger by writing some articles.
Hope you‘ll like it, above are just my personal opinions, 加油！！:)