Hey, nicely written! I can't type simplified so I typed in traditional. You can use google translation or other dictionary if there is any characters you can't recognize 

(1) It is also ok to say 你好 but it sounds more natural to use 大家 here for me, because you are talking to more than one person here. (there might be more than one reader to this post)

(2) The subject for the whole sentence is 我, so 現在 sounds more natural to be put after the second 我. By the way, the second 我 is optional.

現在 can also be put in front of 我 if the main point here is focused on time. For example, 昨天我還在澳大利亞，可是現在我已經在加拿大了(I was in Australia yesterday, but I am in Canada now)

(3) The pluralness is already understood by 很多, so we should not add a 們 here. Unlike English, plural is usually not required to be agreed upon grammatically or even be indicated.

(4) The whole sentence sounds weird even if spoken in English. I think you want to say "They sometimes talk in Chinese and  I also want to chat with them", which would be 他們有時候說中文，而我也想能跟他們聊天

(5) Again, this sentence sounds weird not because of grammatical reason. I think 我去年畢業了，可是我現在還沒有工作 (I graduated last year, but I still don't have a job now) is what you want to say.

大家好! 我叫Alice，我的中文名字是诗含。我是澳大利亚人，但现在我跟我的男朋友住在加拿大，我男朋友是中国人。我想学习汉语，因为我男朋友的爸爸不会说英语。当然我也有很多中国朋友，他们有时候想说汉语，所以我也想跟他们用汉语聊天儿。

我去年大学毕业了，我的专业是环境学，但目前还没有工作。

我的兴趣爱好是做饭,、看书和去露营。

A Brief Introduction

他是中国人。我想学习汉语因为我男朋友的爸爸不会说英语。我也有很多中国朋友们。他们有时候相说中文所以想跟他们聊天儿（他们有时候说中文，我想跟他们聊天儿，所以我想学中文。）。
现在我没有工作可是去年我毕业了。（我去年毕业了可是现在没有工作。）我的专业是环境学。
我喜欢做饭, 看书和去露营。

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No obvious mistakes. You writes well !!