Проверьте ошибки (англ. язык)

I would like to tell you a story about my friend's family.
My friend’s name is Nikita. Nikita is a programmer. He is 45 . Nikita often sings and when he is at home and has some free time he plays the guitar. Once when he was small his family went to a lake. It was a sunny warm day. And the lake was so nice that they wanted to swim. His elder brother offered Nikita to swim.
He was good at swimming so he headed straight for a deep part. Nikita couldn’t swim well, but in order to show that he was brave he followed his brother. Suddenly Nikita felt that his legs became so heavy and he couldn’t move. He was in panic and started to shout for help. He fainted and started to drown. When he opened his eyes he was lying on the beach and his brother was trying to revive him. Everything ended well, but these frightening memories have become his phobia and he never swims.
Чуток поправил, чтобы звучало натурально.

Если в первом предложении подразумевается дружная семья то ошибка. У Вас скорее можно понять как дружеская семья (может даже как семья друга, дружественная семья) .
дружный 1) friendly дружная семья — close(ly)-knit/united family

I would like to tell you a story about my friend’s family. His name’s Nikita. Nikita is a programmer. He is 45. Nikita often sings and when he is at home and has some free time he plays the guitar. When he was little his family went to a lake. It was a sunny and warm day. And they wanted to swim a lot. And his elder brother offered Nikita to swim.
The brother was good at swimming so he moved straight to the deep side. Nikita swam badly, but in order to show everyone his bravery he went with his brother. Suddenly Nikita felt that his legs become so heavy and he couldn’t move. He was in panic and started to shout asking for help. He lost his consciousness and started drowning. When he opened his eyes he found himself lying on the sand and his brother had already called an ambulance. These frightening memories became his phobia and he’d never swum since that day.

согласен с мегамозгом (у него отличный вариант) , но тож подправил на свой вкус и цвет)
выбор за вами))

When he is at home
Лучше сказать When he was young
скажи лучше He tought Nikita how to swim
he couldnt
He was afraid
Became his phobia and he never wanted to swim