Can someone help me understand this Russian sentence?
Ты должен заехать за ней на работу, отвезти к себе, а у тебя дома уже готовый со свечами и ужином.
I can't understand the first part. "Ты должен заехать за ней на работу"
I know someone has to do something but the problem is that I can't understand the role os these prepositions and the cases, which prevent me of understand this sentence.
You must drive to work to pick her up.June 2018
It's за + instrumental, which is used among other things to express something that you aсquire:
Она вышла за газетой. She went out for (to get) a paper.
Он заехал за мной. He stopped by for me.
Он пошел за бензином. He went for (to get) gasoline.
Literally it means behind or beyond:
Паша стоит за мной. Pasha is standing behind me.
Его поля за лесом. His fields are beyond the woods.
Даря живёт за городом. Darya lives outside town.June 2018
In this context, заехать means 'to get someone from somewhere' or 'to stop for something somewhere'.
Preposition за ( + instrumental case) refers to someone/something you want to get or stop for.
Prepostition на/в ( + accusative case) refers to a place where you want to stop at.June 2018
You should pick her up at work, take her back to your place where the table is already set with candles for dinner. Good luck!June 2018
‘ехать ...на работу’ is standard for ‘to drive to work’ ‘заехать’ means ‘to drop by for a short time (in a car)’ ‘заехать за ней’ means something like ‘drive over to see her for a short time’, so “заехать за ней на работу» means “drive over to see her at her workplace for a short time”.July 2018
I have to object to it.
"Заехать за ней на работу" is 'to drive to her work and take her to somewhere else', not just 'to see her for a short time.'
Some similar examples:
Он зашёл за мной, и мы пошли вместе в кино.
Жена говорит мужу: Ты не мог бы заехать за детьми в детский сад и отвести их домой?
However, the second meaning of this word эto go for a short time, by the wayэ, exists as well:
По пути домой я зашел в магазин, чтобы купить молоко для ребенка.
По дороге из Берлина в Москву мы заехали на пару дней в Минск.July 2018