The answer will be next week or after.
Could you call us again on or after August third?
My dad forbids me from going out after 9 p.m.
Everything that happened since you descended some stairs, is hereafter. It's all after the stairs thing you did, since you did it already.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.