Out on a limb means : Do something  risky
Out of the blue means : Happen unexpectedly
Open the floodgates means : Release something that was previously under control
Let sleeping dogs lie means : Leave something alone if it might cause trouble
Kill two birds with one stone means : To solve two problems at a time with just one action
Keep something at bay means : Keep something away
Last straw means : The final problem in a series of problems
It takes two to tango means : Both people involved in a bad situation are responsible for it
Knock out means : To win by hitting another one
Keep up with means : To keep pace with
Keep off means : To ward off
Hold to means : Abide By
Hold out means : To Endure; To Refuse to yield; To continue; To offer
Hang upon means : To depend upon
Hang about means : To Loiter near a place
Go by means : To follow
Go without means : To remain without
Go Down means : To be accepted
Go after means : To Follow; To Pursue
Give over means : Not to do any longer
Give in means : To Surrender; To Yield
Get into means : To be involved in
Get on with means : To Live Pleasantly Together; To Progress
Get along means : To Prosper; To Progress; To Proceed
Fall under means : To come under
Fall off means : To Withdraw; To Drop Off
Fall down means : From a higher position to a lower one
Fall back means : To Recede; To Retreat
Drop out means : To fall
Drop in means : To Visit Casually