Student Insurance New York

I am a United States Citizen who has been living in Germany for around 10 years, I will be studying at Columbia this Fall but I have major problems with the health insurance. One problem is I can’t even access the New York health government website, I don’t know if this is because I am out of the country, I would assume so. Another issue is that I don’t know if the basic New York health insurance qualifies me for a waiver, or I need a special plan. I am a low income student so I am trying to not have to pay the Columbia’s automatic insurance that for me is unaffordable. Next is the issue of timing. In Germany when you sign up for health insurance it is pretty much automatic, it does not take months to become active, it’s pretty quick but then you are paying for it- I made the mistake of thinking it would be similar so I waited until the month before to enrol. It turns out that when I enrol today my insurance won’t begin until the next month, but Columbia wants prove that I am insured from the 15th of this month until next year to wave the plan. I am insured in Germany now, but this won’t work for me after leaving the country. I was told by the office that I could have some sort of letter- does anybody know how to navigate this? If anyone knows anything I would be so eternally grateful since this is really stressful. I reached out to the office and they weren’t very helpful. Thank you.