To not make head or tail of something
to not understand something at all
To beat about/around the bush
to talk around a difficult topic
To fall through the cracks
to miss something important
To hear something through the grapevine
to hear a rumour
To get straight to the point / to cut to the chase
to speak directly to someone
Like talking to a brick wall
talking to someone that doesn't listen; very stubborn
To keep someone in the loop
to keep them updated with the latest information
To put someone in the picture
to tell them something they need to know about
In a nutshell
To summarise the main idea
To have the wrong end of the stick
A misunderstanding
To be on the same wavelength as someone
to think in the same way
To talk at cross purposes
To talk about different things without realising it
To get it straight from the horse's mouth
to get information directly from the source