**CORRECTIONS**

So sad!
Korean adult men must serve the army.
>> So sad! Korean adult men must serve *in the army.

Before going into it, they have the health medical check to get confirmed wheather they are able to stay in the army.
>> Before going into it, they have *a health medical check to get confirmed *whether they are able to stay in the army.

So my son went to the army 3 months ago.
>> Correct sentence.

I also had been to it long time ago and I had some problems there, such as mental pain, adaptation and groupe life disorder.
>> I also had been to it *a long time ago and I had some problems there, such as mental pain, adaptation, and group life disorder.

My son has the same problems now as what I experienced.
>> My son has the same problems now *like what I've experienced.

But parents have do nothing to him except that encourage him when call each other.
>> But as parents have *done nothing to him except to encourage him when we call each other.

I believe him to solve this difficulties and adapt the mood for the army.
>> I believe he can solve these difficulties and adapt to the mood in the army.

I only wish time to go quickly untill seeing him again.
>> I only wish time to go quickly until seeing him again.