Breakdown of Вчера вечером он долго был в душе.
он
he / it (for a masculine noun) / it (for a neuter noun)
вечером
in the evening
в
in / to (direction)
вчера
yesterday
Questions & Answers about Вчера вечером он долго был в душе.
Why is it вчера вечером and not just вчера вечер?
To express that something happened during the evening, Russian changes the word вечер to вечером. This is called the instrumental case. So вчера вечером naturally translates to yesterday in the evening.
We are learning about reflexive verbs like мыться (to wash oneself). Why isn't a reflexive verb used here?
You could use a reflexive verb and say он мылся (he was washing himself), but this sentence specifically focuses on his location. Because he was physically in the shower (в душе), we simply use the verb был (was).
Why does душ (shower) have an -е at the end here?
Because he is located in the shower, we use the preposition в (in) with the prepositional case to show location. The word душ is a masculine noun ending in a consonant, so it takes the standard prepositional ending -е, making it в душе.
Can I use a word like длинно instead of долго to mean for a long time?
No, the adverb долго is used exclusively for a long duration of time. Words built from длинный (long) are used to describe physical length, like a long street or a long line.