My first pet

When I was 10 years old my mother finally bought me a pet, it was a fish. I was very excited because it was my first pet, so I took care of it very carefully, but one day I found the fish had died. After that I never wanted any kind of pet. I think it was like a trauma.

Simple but clear, and just a question of the verb tense, and punctuation.

My first pet

When i was 10 years old my motherfinally bought me a pet, it was a fish. I was very excited because it was my firs pet so I took care of it very carefully, but one day I found the fish died. After that I never want any kind of pet. I think it was like a trauma.

My First Pet

When I (i)  was 10 years old, my mother finally bought me a pet, it was a fish. I was very excited because it was my first (firs) pet so I took very great care of it (very carefully,). One (but one) day I found the fish had died and after that I never want any kind of pet. I think it was like a trauma.