Hair transparency problem

I combined a ponytail and bangs from another hair into one, it took a lot of time, but I finally finished it. But there were a little glitch. A part of the bangs is visible from behind, like the ponytail would be transparent. Firstly I thought it's fine, but in the game it's quite irritating.

I searched for tutorials, but I don't understand those that I found : /

If someone could explain to a beginner what to do, I'd be very thankful