Half-life 2 Episode two sound problem and bug problem

Hello

I have a Half-life 2 episode two sound problem and bug. Whenever Alyx speaks at the beginning, no sound comes out of her mouth. The problem began when I intalled it the first time, there were no poblems except that bug problem where the white words appear at the top of the screen. Then I downloaded another one and installed i but it did not work so I deleted that one and replaced it accedentally on he first one . So I came back to the original one and installed it again. Then the poblem began, no sound was coming out at all. Then I deleted it and installed it again, this time only the backgound sound. Finally, I deleted it and installed it, the same problem, background sound only came out. So please can anyone fix my problem and tell me what to do.

Thank you