после = after через is used with time. For example: I will be there in 15 minutes = Я буду там через 15 минут. I hope everything will change in a month = Надеюсь, все изменится через месяц. до и перед = before I will try to explain the difference between them in examples: вернуться до начала фильма (to return before the film starts = you can return any time before it) вернуться перед началом фильма (to return before the film starts = you can't return any time, you need to return right before it starts, maybe 5-15 minutes before) If you want to use "before" with hours, week days, months, years in the meaning "to do something before...", use "до" Example: я должен навестить родителей до 5 часов/до понедельника(etc.) I have to visit my parents before 5pm/Monday (etc.)

после = after for example: - после обеда = after the dinner, - после праздника = after the party. через after the word "через" almost always is a number. for example: - через 5 минут = in a 5 minutes, - через два дня = in two days.

Посмотрите ответы тут: https://www.italki.com/question/156302