Теория:

Выражения "at/in the beginning", "at/in the end" и их употребление в речи.
At the beginning \(+\) of sth — в начале чего-либо.
Пример:
There is a picture at the beginning of the book.
You’ll see a church at the beginning of the street.
In the beginning — вначале, сперва (предполагает последующие изменения).
Пример:
I enjoyed my job in the beginning, but I'm bored with it now.
I thought it would be hard in the beginning, but now I find it easy.
At the end \(+\) of sth — в конце чего-либо.
Пример:
I felt very tired at the end of the day.
There was a church at the end of the road.
In the end — в конце концов, в итоге.
Пример:
We wanted to take the train, but in the end we got a taxi.
In the end, I saw that she was right.