Hi Khadgar42,

this topic has been discussed a while before: Both Text + Speech Option ?

To make things short: There were two different versions of the game, one with text or speech only, and the other one with the option to have both. GOG seemingly is distributing the one without the latter option.

There are ways to make it work any way, a bit further into the discussion. But they look quite complicated and also don't work that well. But maybe you can give it a try.