Past perfect (+) s + had + V3 / V ed + c + M s + had + not + V3 / V ed + c + m (?) Had + s + V3 / V ed + c + M?

At the end – at the finishing point of something
In the beginning – at first, in the early stages
In the end – at last, eventually, finally
e.g. It would be great if we discussed some news at the beginning of our lessons.
At the beginning of the meeting, the boss introduced the issues.
At the end of the performance, the actors went to the stage and thanked to fans.
In the beginning, they thought it would be easy to study in Foundation 2, but after seeing topics they realized that it wouldn’t actually so.
In the beginning, we hated each other, but now, we are so close that we are ready to sacrifice each other if it is needed.
At the beginning of the match, Real Madrid was winning the match, but in the end, Barcelona was winner.

On is used before exact days and dates.
On Monday / on the second of July
e.g. On the 25^th of august Foundation 2 students are having an exam.
On Sunday, we are going to play billiards.
On / at / in July, 2, 2009
On / at / in May, 1997

On time – at the arranged time, not before or after it.
In time – not late, 5 – 10 minutes earlier.
In good time – early with comfortable margin, 15 – 45 minutes earlier.
e.g. The exam started on time.
Students come to the lessons in good time, teachers come in time, the lessons start on time.
Before
Before can be used as an adverb, preposition and conjunction.
e.g. Have you eaten caviar before?
Today, I woke up before 5 o’clock.
Tom told an answer before me.
They had already gone home before I arrived.
Before I finish my homework, I will not have dinner.
Since
Since can be used as an adverb, preposition, and as a conjunction.
e.g. Sam left home five years ago. His parents haven’t seen him since.
We have been working together since November.
Tom hasn’t contacted me since he moved to another city.