a simple sentence.

你好。我在一个人学习汉语。我爱汉语，有一天我会去中国。

Hello. I am learning Chinese by myself. I like the Chinese language and one day I'll to China.
be + verb+ing, most of the time can be translated into “在做什么事”
Note used both traditional and simplified characters.

Traditional and simplified Chinese doesn't have much difference in terms of grammar. They only differs at the spelling.

你好。 我是漢語（汉语）一個（个）人 學習 （学习）。 我愛（爱） 漢語（汉语）和 一天，我去中國（国）。

Hello. I am learning Chinese by myself.

你好，我自学汉语。

TIPS：

“Learn sth. by oneself":

learn=学习 xué ，oneself=自己 zì jǐ ，by=通过tōng guò（We usually don't translate it.）

自己学习sth=自学sth=Learn sth. by oneself

I like the Chinese language and one day I'll to China.

我喜欢汉语，有一天我会去中国。
TIPS：

1，"one day":

one= 一 yī ，day=天 tiān  

But we translate it for “有一天yǒu yì tiān /总zǒng有一天” here bcause it represents what will happen in the future.

2，will

It represents the future tense，we translate it of “将要jiāng yào   /会huì ”

Learning a new language is very interesting, and it's very difficult.
If you need any help, you can ask me.
Welcome to China。 China has many beautiful scenery, also has many friendly friends.

a simple sentence.

你好，我在自学汉语，我爱汉语，总有一天我会去中国

learn something by oneself ---------一个人学习------------自学

Hello. I am learning Chinese by myself. I like the Chinese language and one day I'll to China.

Note used both traditional and simplified characters.

a simple sentence.

Glad to see your progress in Chinese. It seems you have learned some Chinese words, and you are still not good at placing them in a right order, but it's not a problem when you can write or speak to a native speaker daily.