When do I have to use "that"?

[Nightmare85]

Hello,
Once I learned that we do not have always to use that in such sentences.
However, I have never understood it :-o

I know that I'm right. - no that
I think that you should go. - no that
All songs that I hear remind me of her.
In my opinion it is bad that he leaves our firm.
I believe that it's a great idea. - no that
Do you really think it's good that you wear this?

I've already written a - no that behind some sentences where I believe that should not be used.

Cheers!

 

[bhaisahab]

Hello,
Once I learned that we do not have always to use that in such sentences.
However, I have never understood it :-o

I know that I'm right. - no that Optional.
I think that you should go. - no that Optional.
All the songs that I hear remind me of her. Optional.
In my opinion it is bad that he is leaving our firm. Necessary.
I believe that it's a great idea. - no that Optional.
Do you really think it's good that you wear this? Necessary.

I've already written a - no that behind some sentences where I believe that should not be used.

Cheers!

.