how to use "jie shu" in a sentence?

Kai shi can also mean "begin"
Here's some examples...

1. "The lesson has just started/ended"
课堂刚刚开始/结束了
ke tang gang gang kai shi/jie shu le

The "ke tang" here means "lesson(s)" and "gang gang" means "just"
You can actually replace the "ke tang" with any other nouns that fit the meaning

2. "The end is the start of another"
结束是另一个开始
jie shu jiu shi ling yi ge kai shi

The "ling yi ge" here means "another".

I hope you understand:{ sorry for my broken english

结束 means ended
开始 means started

our love relationship has ended
wo men de ai qing yi jing jie shu le.
我们的爱情已经结束了.

the competiton has ended
比赛已经结束了.
bi sai yi jing jie shu le.

to end this distratous love, I killed her.
wei le jie shu zhe duan nie yuan,wo ba ta gei zuo le.
为了结束这段孽缘,我把她给做了。

这在是我想要的开始。
This is what I wanted for start .
zhe zai shi wo xiang yao de kai shi

你的痛苦才刚刚开始.我一定要把你折磨的人不是人,鬼不是鬼。
ni de tong ku cai gang gang kai shi,wo yi ding yao ba ni zhe mo de ren bu shi ren, gui bu shi gui.
Your torment have just started.I will make sure to torture you untill you don't feel like ghost or human.