When you're on a conference call in English, you want to be sure you have understood the other people on the call. Sometimes though, it's difficult to understand native English speakers. You also need to make sure what you are saying is clear.
There is one trick you need to know, and that is sentence stress.
Sentence stress means that when someone is speaking, you can hear all of the important words. The less important words get much shorter and sometimes totally disappear. (Have you ever thought English speakers are eating their words? They really are!)
So if you hear the important words, you can usually understand the meaning, even if you didn't hear all the unimportant words in between.
You also need to use sentence stress yourself to deliver your message clearly. Make sure all the important words are slightly longer and louder. You can practise this by reading aloud and exaggerating the words that bring meaning to the sentence.