Increasing speed of creating object every x second

hey

im trying to create this game that avoiding the objects

i want to increase the speed of creating object every x sec. because i increase the speed of the blocks with a behavior of bullet, lets say in every 5 sec i add +20 in speed of 300.

lets say in first 5 sec the gap of each block is 1 meter cuz it has a speed of 300 and creating time is 1 sec.

but after like 25 sec the speed is 400 and gap is 2 meters already with creating time in 1 sec. i want the distance of it doesn't affect overt time, im very new in here.

Best way would be to have another variable "speed factor"

then speed = base speed x speed factor

and

interval for generating blocks is x seconds / speed factor.

then speed and block creation will allways match...

I think... my maths not to great but it sounds right....