قبل أن وبعد ان
Are used in the formal Arabic but not in the daily life
قبل ما وبعد ما
Are what we use in our daily life as a slang
Ex) I will go home after finishing my job
سوف اذهب إلى المنزل بعد أن أنهي عملي
(That's how it can be said as formal)
هروح البيت بعد ما اخلص شغل
(That's what we say in Egypt and the slang in every Arabian country is different from each other)