你好～

亲爱的日记：你好！
今天早上我去学校。我有两节课，数学课和英语课！我觉得数学很难，可是我的老师教学办法很好！所以我学很多。
今天天气很热，我最喜欢热的天气。我不喜欢冬天，因为冬天天气很冷！
我很累，昨天晚上 我学睡觉太晚了！

。 。 。 糟糕！ 我忘了！星期一我有中文课考试！我需要复习很多～

再见！

朱丽叶

Here is my suggestion:

學校 replace by上學。Your sentence is make sense.However, 上學 can be much better. To me,我去學校 。I will prefer when people ask me:where are you going, then I will answer in 我去學校。

可是 replace by但是。In my opinion,可是 in Chinese means :Well.... something something. I pick 但是  because it exactly means however in Chinese.

教學方法很好 replaCE by 教得很好。My teacher's teaching method is so well compare my teacher teaches so well. 我的老師教得很好 already express your meaning. In the Chinese writing, you don t need to make a complicate sentence. Try to use the short phrase to express your idea. Remember, simple is the best.

學很多 add 到了=學到了很多， I think this one is hard to explain. However, I will try my best. 學很多=learn a lot. For example,我學很多語言(I learn a lot of languages)。到了 means arrived to somewhere.我學到了很多( I m fully understand after I learn from my teacher.) In this situation,到了 means I attach my goal and fully understand.

熱的天氣 replace by 夏天( summer): I understand why you are using hot weather. You are typical American girl,haha.However, it sounds weird in Chinese. In Chinese people's mind, when you say 夏天which already means hot weather. That's why I try teach you sounds as a Chinese.

昨天我學睡覺太晚 replace by因為昨天晚上我複習到很晚才睡覺：I think you try to say I slept quite late because I studied last night. If you read the sentence that I write it. You will learn the Chinese grammar.因為(because)昨天(yesterday)晚上(night)我(I)複習(study)到(until)很晚(quite late)才(and then)睡覺(sleep).Hopefully, that will help you understand the complex sentence structure in Chinese.

星期一我有中文課考試replace by我還有中文考試在(下一個next/這一個 this )星期一。 I think this structure is similar to English. I still have Chinese exam on (next or this ) Monday. 我(I)還有 (still have)中文考試(Chinese exam) 在(on)下一個(next)星期一(M onday)。 P'S: I never hear people said we have a chemistry class exam on coming up Monday and I only hear we have a chemistry exam (Chem test)on comming up monday. Same idea in Chinese.

我需要複習很多 replace by我要努力複習考試：I guese you are trying to say I need to do a lot of study. Key word in here is努力(strive). This is a frequency word in Chinese. In the Chinese people mind, 努力 also mean do the best and do a lot. It is a motivated word to do something. 我(I)要( will)努力(strive)複習(study/review)考試(exam).

Julie, it s a good start for you to write the journal. Practice will make you sounds so Chinese in one day. I hope my translate and explain can helping you , have a nice day^^

你好～

亲爱的日记：你好！ ( good! )
今天早上我回学校。（ good! ）

我有两节课：数学课和英语课。（you should use ":"  colon, if you use "," , in this way:" 我有两节课，它们是数学课和英语课。"）

我觉得数学很难，不过我的老师教学方法很好！（教学方法 is better）

所以我学会了很多。 

今天天气很热，我最喜欢大热天了。（we usually say 大热天instead of 热的天气，it's more fluent）

我不喜欢冬天，因为冬天很冷！ (we often ignore"天气" in these sentences, such as: 春天很暖和，夏天很热，秋天很凉爽，冬天很冷。)
我很累，因为昨天晚上我太晚睡觉了！ （do you mean you stay up late for studying last night? If yes, it can be: 我很累，因为昨天晚上我学习到很晚而太迟睡觉了。）

。 。 。 糟糕！我忘了星期一我有中文考试！（中文考试，pls ignore "课"，for example: 数学考试，英语考试，语文考试，体育考试 ect.)

我需要复习很多东西。（ 东西 this word is interesting, it has many defferent meaning. here 东西 means 考试内容。）

再见！

朱丽叶

Dear Juliet, hope my suggestions can help you. ......梁山泊（Laker）

你好～

亲爱的日记：你好！
今天早上我去学校。我有两节课，数学课和英语课！我觉得数学很难，可是我的老师教学办法很好教得很好！所以我学到很多。
今天天气很热，我最喜欢热的天气。我不喜欢冬天，因为冬天天气很冷！
我很累，昨天晚上 我学睡觉睡得太晚了！

。 。 。 糟糕！ 我忘了！星期一我有中文课考试！我需要复习很多～

再见！

朱丽叶

Your Chinese is good.

 If you have any Chinese grammar problem, you can ask me.

你好～

亲爱的日记：你好！ 

今天早上我去学校。我有两节课，数学课和英语课！我觉得数学很难，可是我的老师教学办法很好！，所以我学了很多！

今天天气很热，我最喜欢热的天气。; 我不喜欢冬天，因为冬天天气很冷！

我很累，因為昨天晚上我学中文，睡觉太晚睡觉了！
。 。 。 糟糕！ 我忘了！星期一我還有中文课考试！我還需要复习很多課堂資料～

再见！

朱丽叶