The construct that you are trying to form is called a conditional.
The first sentence is in simple past and the second sentence is in simple present, so the 2nd conditional is what you need.
If I didn't learn Chinese as a child, I wouldn't be able to write it.
You only need to use the 3rd conditional if you want to imagine what would have happened if the past were to have been altered. Also, here's some additional notes I wrote describing the three conditionals.
1st conditional: Present -> Certain Future
If I buy a pizza, I will need to spend money.
2nd conditional: Unreal Present -> Future or Unreal Past -> Present
I don't have a million dollars. However, if I had a million dollars, I would invest it in hedge funds.
I went to elementary school. I am in high school. However, if I didn't go to elementary school, I wouldn't be in high school.
3rd Conditional: Unreal Past A -> Hypothetical Past B
I didn't buy car insurance. I was in a lot of trouble.
If I had bought car insurance, I wouldn't have been in a lot of trouble.