Here is my self-introduction.

-> This sentence is okay.

Please check my sentences.

-> Correct sentence

My name is Lee Kwang-Seok.

-> This is a good way to start an introduction. The sentence is also right.

I am a 41 year old, happily married father of two.

-> Good sentence. You tried to induce interest here by adding more information and not cutting the sentence short.

Currently, I am a salesman in the Smart Tower Team of Samsung SDS.

-> Good sentence

It is a position I have held for 14 years.

-> This sentence is okay.

My main responsibility is to preside over sales from abroad.

-> Excellent sentence

Prior to working for Samsung SDS, I was in charge of product design for Samsung commercial vehicles (SCV) for 3 years.

-> This one is impressive because you used a transitional device to start a sentence.

I have completed my military service, during which I was an artillery officer in Hwacheon for 28 months.

-> This is a very good sentence.

I graduated from Gyeongnam University, majoring in machine design.

-> This is also correct.

I am a confident, friendly and outgoing guy who likes to meet new people.

-> This is a right sentence. However, you have the clause "I am" in the last two sentences. You might need to change either to avoid overusing it.

-> You can say "Aside from being a confident, friendly and outgoing guy, I also like to meet new people."

When I am not working, I like to go for walks and spend time with my children.

-> Good sentence.

-> You may use "When I have free time, I like to go for walks and spend time with my children."

>>>>>> I am really impressed with this composition of yours. I did not find any grammar or spelling errors. I just noticed that you need a little improvement in using transitional devices. Still, this self-introduction is commendable. I appreciate your effort in sending this and I wish you could apply the same ability in our class. Thank you and keep up the good work. :)

~~T. Liz