HSK3 汉字 (126-130)

极
极少数人民住（活）超过了一百年（岁）。

极少数人活过了一百岁，

活alive, 我还活着 I am still alive, 我住在中国 I live in China.

岁year, for people, 年year , for something
Very few people live more than a 100 years.

普
普通话，汉语，中文，都一样。
The common dialect, Mandarin and Chinese are one and the same. 

Good job！
 
境
这所工厂的产品是出境（口）。

出境，(people) go abroad ,  出口, (productions ) are exported
This factory's products are exported.

楼
健身房在下楼(楼下)。

楼下 downstairs。 下楼 go downstairs
The gym is downstairs.

满
他对生活很满足。
He is satisfied with his life.

This scentence is ok.

HSK3 汉字 (126-130)

极
极少人活到100岁以上。I suppose you're talking about people's life expectancy.
Very few people live more than a 100 years.

普
汉语，普通话，中文，都一样。 What do you mean by 'common dialect'? The language Han nationality(汉族) speak?
The common dialect, Mandarin and Chinese are one and the same.

境
这所工厂的产品用于境外销售。Do you have to use '境'? If not, you can say 这所工厂的产品用于出口。
This factory's products are exported.

楼
健身房在楼下。 下楼 means one goes downstairs.
The gym is downstairs.

满
他对生活很满足。
He is satisfied with his life.

HSK3 汉字 (126-130)

极
极少数人民住超过了一百年。 很少人能活过一百岁 would be a more natural translation of the English.
Very few people live more than a 100 years.

极 means exceedingly, to the limit, ultimate, etc 极好良品不便宜 exceedingly good products are not cheap.

普
普通话，汉语，中文，都一样。
The common speak dialect, Mandarin and Chinese are one and the same.

Though 汉語 and 中文 means the same, they are used differently.  汉語 is used more in the context of comparing Chinese against languages that use Chinese script too, such as Japanese or Korean. Another cultural note, the way you said it means that other languages such as Cantonese or the Wu, are not Chinese languages. It would be like telling a Quebecois what he is speaking is not French.

普 =  general / popular / everywhere / universal

普渡众生 = universal salvation,

普遍天地 all over the heaven and earth = extremely common

境
这所工厂的产品是出 口的境 。
This factory's products are exported.

沒有护照不能入境 No passport no entry (into a country)

天下境界多多 Too many borders in this world

由於境况不好, 很多人失业 Due to unfavourable (economic) conditions, many people lost their jobs

楼
健身房在下楼下。
The gym is downstairs.

满
他对生活很满足。 perfect :) He is very satisfied with life.
He is very satisfied with his life. 他对自己的生活很满足  As you as see, with your English version, I can help you with expressing the exact nuances of your thoughts :)