Im watching this video but since its in german I dont fully understand the way it works, specially the startup side with the pulse source and the mosfet.
Could someone explain me this part of the circuit, please?
It's not really a complete converter, they're just simulating the switch and output. The VCVS E1 just floats the pulse waveform to drive the MOSFET gate.
It has a fixed frequency of 20kHz and a fixed duty cycle of 0.6.