I won't correct what others have done but I will explain to you their correction.
#1 Chinese sentence pattern is as follows:
Subject + time + (verbs of desire) + location where the action is performed + verb (object).
I (我) + time (omitted) + desires (想要，想） + location (在学校) + action (学汉语) . This is important to remember when trying to translate a sentence.
#2 要 means you are definitely going to do something. 想要 and 想 expresses that you desire to do something but there is no definitely going to meaning.
My School
我要说中文在学校。 但是我的学校没有班级的中文。
我的学校有班级的西班牙语和班级的日语。
wǒ yào shūo zhōngwén zài xuéxiào. dànshì wǒ de xué xiào méiyǒu bānjí de zhōngwén.
wǒ de xuéxiào yǒu bānjí de xībānyáyǔ hé bānjí de rìjǔ.
Translation: I want to speak Chinese at* school.(我要在学校说中文) However,（但是） my school doesn't have Chinese class.（我的学校没有中文课程）
My school has Spanish and Japanese class.（我的学校有西班牙语和日语课程）
*I don't know how to say 'at' so I used 在 zài (location indicator) instead.
class:课程or班级 ；we translation 课程 here
My School
我想在学校说汉语。但是，我的学校没有汉语课。
我的学校有西班牙语和日语课。
我要说中文在学校。 但是我的学校没有班级的中文。
我的学校有班级的西班牙语和班级的日语。
wǒ yào shūo zhōngwén zài xuéxiào. dànshì wǒ de xué xiào méiyǒu bānjí de zhōngwén.
wǒ de xuéxiào yǒu bānjí de xībānyáyǔ hé bānjí de rìjǔ.
Translation: I want to speak Chinese at* school. However, my school doesn't have Chinese class.
My school has Spanish and Japanese class.
*I don't know how to say 'at' so I used 在 zài (location indicator) instead.
You can also use 没有 to make comparision …
She is not as beautiful as you.
她没有妳的漂亮。
He is not as tall as Wang.
他没有小王高。
Noun + 没有 + Noun + adjective. The first noun possesses less adjective than second noun.
#3 this is a 有/没有 sentence. It's pretty simply, just say some place has or not have some thing. My school has （有）Japanese and Spanish classes but do not have （没有）Chinese class. Since the subject is the same in both parts of the sentence, the subject should not be repeated.
