You just set the date 1st, then using the internally recessed pushpiece to set the day of the week, so like today is Tuesday the 15th. So you just synchronise them.
The day starts on Monday bro, if you see the bottom it's Montag, and then ends on SUnday, which is in red. What were you referring to to say that it starts on saturday?
It won't have a screw-down crown, no current nor past Lange does. Maybe one day in the future, but just not yet.
Cheers
Stephen