I am 19 years old man living in South Korea.
I want to invest in bitcoin for rest of my life, and I have 0.002 btc now. I want to keep it safe forever.
Someone told me that exchange is not safe because exchange can be hacked by hackers.
I am using software wallet called 'electrum'. I downloaded it from the official website 'electrum.org'
Is this safe wallet?
Sorry, I am not fluent in English. Please understand me.
You are not a man bro you are just 19 years old which means you are still a teenager

and yeah you are from South Korea so you have some difficulties in English for that, I am recommending using a Grammer checker so it will check and correct your post.
Talking about the wallet, my suggestion is to use the Electrum wallet, many other members also mentioned the Electrum wallet to you because they all know that for saving your hard-earned bitcoin electrum wallet is best in a sense of security. I have been working since 2011 and still has very powerful security features. Many of the experienced people also recommended Electrum wallet. Above there are many other replies to you read them and then take the decision.