HSK3 汉字 (66-70)

演
这是他们最好的表演了！
That was their best performance!

感
我对古代史很感兴趣。
I am interested in ancient history.

又
新加坡又热又潮湿。
Singapore is hot and humid

选
在澳大利亚，每个人都得参与选举。
It is mandatory for people to vote in Australia.

闻
这已经是昨天的新闻了。
This is already yesterday's news.

（这里，“已经”是副词，“是” 是动词，所以副词应该放在动词的前面。）

HSK3 汉字 (66-70)

演
这是他们的最好表演了！

这是他们最好的表演了！【You can always put the 的 right before the noun you are modifing】

That was their best performance! / It also means, This is their best perfomance. ie: don't expect more. 

感
我对古史很感兴趣。  我对古代史很感兴趣。
I am interested in ancient history. 

Although it's fine to say 古史, because there was a significant movement among the Chinese historians in the 20th century, which is called 古史辨运动, in which they questioned and tried to rediscover the writing of ancient Chinese history. I'm also intererested in 古代史 btw. 

又
新加坡又热又潮湿。
Singapore is hot and humid.

新加坡这鬼地方真是又热又潮湿。

Singapore this shitty place is really hot and humid...haha. I like Singapore, trust me...

to make it more authentic, you have to curse a place with this kind of temperature LOL. 

选
在澳大利亚，每个人都得选。 在澳大利亚，每个人都得参与选举。or 每个人都得投票。
It is mandatory for people to vote in Australia.

都得+v+O: 每个人都得吃饭；每个人都得上大学。。。。

or sometimes you can say it like a command, for example, 今天开会，每个人都得去。

闻
这是已经昨天的新闻。
This is already yesterday's news.

we can it 明日黄花 sometimes....

HSK3 汉字 (66-70)

演
这是他们的最好表演了！ 这是他们最好的表演了
That was their best performance!

感
我对古史很感兴趣。
I am interested in ancient history.

又
新加坡又热又潮湿。
Singapore is hot and humid

选
在澳大利亚，每个人都得选。 在澳大利亚每个人都得参加投票选举。
It is mandatory for people to vote in Australia.

闻
这是已经昨天的新闻。 这已经是昨天的新闻了。
This is already yesterday's news.

HSK3 汉字 (66-70)

演
这是他们的最好表演了！
That was their best performance!   【“演”和“表演”是两个词。用“演”造句，可以说“这个演员演得很好。”】

选
在澳大利亚，每个人都得选。 【vote在这里是“以投票形式参加选举”的意思。你可以说“。。。，每个领导人都是被人民选出来的。”】
It is mandatory for people to vote in Australia.

HSK3 汉字 (66-70)

演
这 那是他们的最好的表演了！
That was their best performance!

感 = to feel
我对古代历史很有感兴趣。 我感受到古代历史的大影响 I felt the effects of ancient history greatly
I am interested in ancient history.

又
新加坡又热又潮湿。
Singapore is not only hot and but humid too .Your Chinese sentence here is perfect.  From your original version, 新加坡是熱, 是潮湿 but not natural in Chinese.

选 = option, to choose
在澳大利亚，每个人都得必要去/选举/投票。           另选他人  = to choose someone else
It is mandatory for people to vote in Australia.

闻
这是已经是昨天的新闻。
This is already yesterday's news.