and i wanna execute him in groups of 3 , i mean he execute bang 1 , bang 2 and bang 3 after it finish the next 3 commands it will be executed and so on , in groups of 3.
Do you mean to say executing each set of three simultaneously ? ( background) and wait for them to finish before executing next three?
if not so, they are anyway will be executed one by one. no matters set of three!!!
Again, that depends on how they are going to be executed ( sequential or parallel ).
if they are "independent" of each other, you can run them in parallel mode. (taking consideration of how bulky they are to handle the CPU utilization)
if you can only run the script when previous finishes, I don't think you can do anything to make it faster by grouping of them.
Also, if they are taking time, may be you can do something to tune them.