To be head over heels.
completely in love
To get cold feet!
be nervous before a big event
to play something by ear.
do something without a plan
Turn a blind eye.
to ignore something wrong
To cost an arm and a leg
very expensive
Over my dead body!
only when I die
To be thick in the head.
not very intelligent
To have a skeleton in the closet/cupboard.
hidden secret
In the blink of an eye.
very quickly
An old hand!
an experienced person
Break a leg
good luck
To see eye to eye
to agree
It's my flesh and blood.
my relative
Keep your chin up!
don't despair
To put your feet up.
to relax
You are pulling my leg!
You're joking
To have a bun in the oven.
to be pregnant
To stab someone in the back.
to betray someone