It might actually be something relating to a phrase in OP’s native tongue. (I don’t know.)
More often it is simply that English is learned primarily by hearing, and secondarily by spelling. That makes mix-ups of this kind (if it is a mix-up) common. Many full-grown, native-English speakers mispronounce words all the time.
In English, “life and death” is always meant as something exceedingly consequential, even when used metaphorically. And people will generally NOT like you if you get them to behave differently when no one’s life or death actually hangs in the balance. Just like yelling “fire” in a crowded movie theater.
As always, there are exceptions. Some people speak in almost nothing but loose metaphors, and treat non-trivial stuff as trivial all the time. Their language is often very violent without their realizing it.
Of course, everyone understands the phrase “life and death” to be non-literal when someone is asking a question on a C++ forum.
For those reasons I said nothing. Perhaps OP is trying to repay a debt by helping someone’s kid with English grammar lessons.
Perhaps he (or she) is doing just fine in the world’s most weirdly complex foreign language.