우리는 동갑이야 What my friends and I would say. It means 'we are (of) the same age'.

감사합니다! ^^

A TV series is like what you said where there is the same characters and theme throughout the programme but each week is a new episode with a new storyline. Examples are Modern Family and Friends. A TV serial is usually a fictional story that is 'broken up' into a number of episodes with each episodes usually ending with a cliff hanger. I think most Korean dramas fall into this category with one one storyline but shown in episodes.

Koreans learn American English in school.

N 후에, V-(으)ㄴ 후에: This pattern means 'after a certain period of time' or 'after some action. Somewhat like 'after' or 'later' in English. V-고 나서: This expresses the finishing of one behaviour followed by the beginning of a subsequent behaviour and hence corresponds to 'do (something) after', 'upon finishing' or 'and then' in English. Because -고 나서 expresses temporal order, it can only be used with verbs. If the subject of the first and second clauses are the same in sentences using motion verbs (e.g. 가다, 오다), -아/어서 is used instead. e.g. 나는 학교에 가서 공부해요. (and not 나는 학교에 가고 나서 공부해요). V-아/어서: a connective ending indicating the temporal relationship between events. The action of the second clause occurs after the first clause has occurred. The two actions are so closely related that the second action cannot occur without the first action occurring first. Somewhat like 'and' or '(in order) to' in English. Source: Korean Grammar in Use Beginning

Here is my correction:

 

The temperature of the world has been increasing year by year. Scientists found out that global warming is caused by the amount of Methane and Carbon Dioxide gas in the atmosphere. If we do not do anything, problems will arise. The polar caps will melt and polar bears will lose their habitat. Coral reefs will also die. When coral reefs die, fishes will no longer have food.

We should find solutions, such as riding bicycles instead of driving cars.

Hope that helps!