update: changed my circuit a little bit, now im driving a mosfet from my atmega's pwm output, which (the mosfet) is connected to the transformer.
I hooked up a LED on the secondary side, and sees there, it lights up. Which means, im at least transfering some energy. But when i hook up a small lightbulb, it is not enable to power that. It may be an issue with my mosfets, because they are no logic level mosfets, they are might not "on enough" (logic level mosfets have been ordered, but didnt receive them yet), or my little transformer has to less windings or a combination of these. What do you think?
The picture i attach ive got from my scope, the yellow curve is from the atmegas output, the blue one is from the secondary side of the transformer
edit: i've attached a picture of a similar core, which i'm using, i've wounded 13 turns on each side
edit2: attached schematic of the circuit how it looks like now