A wild goose chase
doing something that may seem impossible, meaningless or pointless
Giving cold shoulder
to ignore someone
Clouds on the horizon
trouble is coming on the way
Let someone off the hook
to let go someone, to not punish or hold someone responsible for something
Feeling under the weather
not feel well; feel sick
Cutting corners
trying to save money or time, by not performing duty or the given task; to skip steps or not do things completely
Go down in flames
to fail in a surprisingly manner
The last straw
the difficulty that ultimately makes the situation worse or unbearable
Break the ice
to get the conversation going
Wrap one's head around something
to understand something that may take a bit of time and effort
Burn bridges
to do something or anger someone to where you cannot go back to how things were and cannot expect help in the future
Your guess is as good as mine
I don't know either
Leave out in the cold
to be ignored or not considered
Keep an ear to the ground
to listen for new information
Run around in circles
to put effort into something while making little or no progress
Scrape the barrel
to make choices you don't want to or normally wouldn't
Having an Ace up the sleeve
to have a hidden or untold advantage
Hook line and sinker
to be deceived completely
Bone to pick
to be angry about something and want to discuss it
Down for the count
to give up or not be able to keep going