Actually, the F.R.B led these schemes not only forin Korea itself, but also for anin other eight nations. Actually, the F.R.B led these schemes not only in Korea, but also in other eight nations.

"another" is singular

Actually, the F.R.RB led these schemes not only forin Korea itself, but also for another eighteight other nations. Actually, the FRB led these schemes not only in Korea itself, but also for eight other nations.

A couple days ago, a currency swap was made between Korea and America,. The F.R.B of the America has led this scheme,; however, the Korean government wants to take credit for this scheme, Itby asserteding that it has led this currency swap. A couple days ago, a currency swap was made between Korea and America. The F.R.B of the America led this scheme; however, the Korean government wants to take credit by asserting that it led this currency swap.

Punctuation. Present perfect doesn't really work, simple past is better for this.

A couple days ago, a currency swap was made between Korea and America, The F.R.RB of the America has led this scheme, - however, the Korean government wants to take credit for this scheme, Itit by asserteding that it has led this currency swap. A couple days ago, a currency swap was made between Korea and America, The FRB of America led this scheme - however, the Korean government wants to take credit for it by asserting that it led this currency swap.

We don't always add periods in acronyms. Examples of this are FRB, USD, UNICEF. It's more common not to put periods after each letter. The FRB is also sometimes referred to as The Fed or the Federal Reserve for short.

The reason why the F.R.B led this scheme is to stabilize world stock markets. The F.R.B led this scheme to stabilize world stock markets.

There is verb tense confusion in the original statement. I felt this was the most natural way to correct.

Just before this scheme was carried outintroduced, the Korean stock market and forex market have beenwere plunging. Just before this scheme was introduced, the Korean stock market and forex market were plunging.

"were" or "had been".

Particularly, Korean markets, in particular, have been unstabilizedle for a week,. Korean markets have faexperienced something like this sometimes, they sayoccasionally; it's called Asian ATM. Korean markets, in particular, have been unstable for a week. Korean markets experience something like this occasionally; it's called Asian ATM.

I'd prefer to leave out "in particular".

When risky situations like this comes, the, foreign currencies will always flow out of Korea,. This kind of thing has happened this time very seriously,time more currency than usual has left. Once athe news of the currency swap came, the markerts of Korea was stabilized successfully, but I meant to say, to be exact, justthey have stabilized for the time being,. The period of the currency swap should last until only six months from now on. When risky situations like this come, foreign currencies always flow out of Korea. This time more currency than usual has left. Once the news of the currency swap came, the markets of Korea stabilized successfully, but, to be exact, they have stabilized for the time being. The currency swap should last until only six months from now.

Fixed the first conditional. If the when in your conditional can be replaced with "whenever" the verb in the condition and the verb in the next clause should be in the same tense. "this kind of thing has happened this time very seriously" sounded weird no matter how I tried to rephrase it, so I feel it works best as a comparative statement. "stabilized successfully" or "were successfully stabilized" sounds more natural.