Why are these flights greyed out?
 

In the FMB under group properties for a selected flight I have say 'Flight 1' with 6 aircraft , 'Flight 2' with 6 aircraft , then flights 3 & 4 are greyed out. How do I have them not so that I could have a flight of 24 fighters in a group?

The same thing for German bombers , only seem to be able to have 9 bombers in a flight so I have to make more . It's really annoying.

No its historic ;)
A german bomber 'Staffel' has nine planes.
A german fighter 'Staffel' has twelve planes.

These numbers can change in historic context, so the fields greyed out.

There is a bug by the Stukas, there should only 9 planes also, but you can select more.

Bomber Command also has no restriction so you can use these two units if you want to create large formations.

Oh ok fair enough.

Well can you copy and paste units without needing to change all the variables all over again? It would just be alot faster then having to add it all manually like flight size , skill , waypoints ect.

one 'trick' you can use for German bombers is to select the 'Type' as stukas- this will give you a Squadron of 3 flights of upto 9 planes each, ie 27 planes.
Totally ahistorical and leads to wrong ac codes but does get a big bunch of bombers together quickly.

Fighter squads are limited to historical (there are instances of more than 12 ac being flown by squads but they are exceptional) limit of 12 ac.

If you want 3 flights of 4 for RAF use Fighter (late) rather than the default 'early which contains 3 flights of 6