我喜歡喝茶。

現在我在喝茶。

但我也很喜歡白茶，和其他種類的茶。

所以我想我只能使用簡單的句子。

並寫很簡單的科目话题。

Which one did you refer to subject or topic？

現在我在喝着茶。

Because my mother tongue is not mandarin, so I always recite this usage： When you use 现在, you should use "着" or "在" here. They both mean "doing".

现在+Subject+在+verb+Object or 现在+subject+verb+着+Object

但我也很喜歡白茶，和其他種類的茶。

Don't forget after your embelished word "茶”

我的普通話很糟糕。

一点也不糟糕，比我的日语好，哈哈

所以我想我只能使用簡單的句子。

“能” means can do。
You can choose whether to use “所以”here. I don't prefer to using here.

或者是/並寫很簡單的话题科目。

1.I think here you use "并" sound a little strange. I referred the dictionary, I think when you use "并", it usually use this usage "verb+并+verb".

Example: 我支持并拥护中国共产党。( I support and endorse Chinese Communist Party.)

I prefer to use "或者是", it means "or".

2.“科目”， did you wanna say "subject", but we use "科目" to describe "major in high school", for example, 英语是高中课程里的一门科目。（English is a kind of major in high school.)

You can say "话题"(topics),here.

哈哈哈哈哈哈

Now I teach you a new word "自重". 自重 means "to be self-dignified".

Using 哈哈哈哈哈哈 is very cute, but 你需要自重！^^||||

Just a joke, don't mind it on your heart!^^