thx for ur reply
im really confused of this
so its something impossible as i guess
Not necessarily impossible as long as we are talking about stepping down voltage, in order to step up amperes.
A transformer is really your easiest, simplest solution.
And for all we know, you could hook up your generator to a 50 Hz 'wall wart' adapter, and it would output 12 V at 8 A. (Or about 100 W, as based on your generator spec of 220 V and 0.5 A, minus losses.)
However it is risky to rush into that. We would need to be sure that the generator runs full power at 50 Hz.
However suppose it runs full power at 40 Hz. This could cause the 50 Hz transformer to (a) saturate, and (b) carry overmuch current, and (c) overheat, and (d) become ruined. That is, if you are not careful.
Now suppose the generator puts out full power at 50 Hz, but less power at lower speeds. Then it is possible things would be all right when you run it at lower speeds into a 50 Hz transformer.
However it is impossible to predict anything without seeing a graph of voltage and current output, versus frequency.
I could be wrong of course, and someone who is more expert might have a different recommendation.