Many of Koreans pronounce '네가' as ' 니가'. But we don't use ' 니가' in a written sentence. 네가 (이 일을) 할래? = Will you do it? 우리가 (이 일을) 할래. = We will do it.

ok, thanks sohn. :)

Yes, the prouncation is almost same. But it is very strict in written sentence. Korean is difficult to me also.

ㅐ ㅔ has the same sound, but the meaning will be different, is it?

The reason why Koreans sound 니가 instead of 네가 is that 네가 sounds almost same as 내가 so it is hard to tell. These two mean the same. 네가 is a subject form of 너(you). 우리 means us and if you use it as a subject, it becomes 우리가.