The jet set consists of people who travel frequently by plane.

In the fast lane comes from motorway (interstate) driving.  Some people live life in the fast lane.

Milling about describes a crowd of people going in all directions at once.

A bit slow in the uptake means dull-witted or slow to understand.  The uptake here is an idea of new information.

Fast forward is a button on audio and video equipment or a story telling device for jumping from one time to a later one.

Fleet of foot is an alliterative phrase describing a good runner, for instance.

Full steam ahead! This reminds me of the radio comedy, The Navy LarkIt is an instruction for a ship to travel forwards at full power.

Ahead of the game is where I like to be with my blog posts.  Then if I am ill or otherwise occupied I can still meet my goals using posts I have written in advance.

At the drop of a hat means instantly.

Dash it!  Is this a dash in writing?  If you make a small mistake a dash might cross it out.  It is a fairly harmless way of expressing annoyance.  Dash also means hurry.

Fast can also mean firmly as in stuck fast, presumably from fastened.  Sheep and goats can become crag-fast if they reach a place they cannot climb away from.

Play fast and loose implies breaking rules or saying one thing and doing another.  Brewer tells of a cheating game at fairs called fast and loose.  The meaning of fast here is fixed.  There is another context where fast and loose are used together in engineering.  There is a fast pulley and a loose pulley.

Another meaning of fast is to go without something such as food.  Because there are no meals during the hours we sleep, the first meal in the morning is called breakfast.

God is slow to anger.  Exodus 34:4-14