@Simsun, @Sergei, unfortunately Pro Mode is not available anymore in Android Pie update for Galaxy S9, S9+ and Note9. A lot of users from different countries are complaining for removal of this functionality. All you can do is to report this issue to Samsung via Samsung Members app.
By removing the Record button and option to use Volume controls for video, they have completely ruined the camera app. You can get 60fps silky smooth video in Android 8, but the Video app now records video that looks like a grainy Sony camcorder. Worse, in fact, and the Pro screen no longer allows record but shows me the picture I used to get with the framerate I set! What on earth? They really have gimped their own camera, why are no vloggers or anyone talking about this?
Please do NOT suggest Open Camera, I have just tried everything it can do and it's the same or worse. Livid. I am going into the shop tomorrow to demand a downgrade, or I'm taking the demo model. I mean that. Livid.