I had my friend look at it and he said the steering gearbox might be corroded. Is this common? Is there any lines by there that may be common for leaking? It loses the whole reservoir of ATF in 3 days, which is strange

 

Most power steering fluid leaks come from the lines or the pump in my experience but the occasional steering gear leak does pop up. Usually it's a seal. You would need to define corrosion and where it is on the steering gear to come to a conclusion.