You really need to hire an accountant. A reputable accountant won't break you, you don't need a major firm or some SV firm, just a licensed accountant. You need them even without revenue because taxes will need to be managed and paid etc. Gusto helps with payroll, but you'd still need to hire a CPA to manage the taxes.
You started a Delaware C corp which means you also have foreign registration fees, business licenses, insurance and things to take care of for your local state. You'd probably be smart to get out of NYC just from a cost perspective although I also understand the desire & benefits it can have. In Florida (that's where I am) or Texas (also lived there), your dollar will stretch further in rents and business licensing is significantly cheaper etc.
The IRS doesn't like the rent thing if you do it improperly, or don't manage the tax implications correctly, they don't care otherwise. They just consider it a benefit which is fine, just needs to be accounted for and reported properly. Use an accountant they will help you set this up to the best of the business and you.
Which is the parent entity? The US one or the Europe based one? Depending where the investment was banked it will also affect your tax issue. Like it or not you will have a more complex tax situation regardless because of the two linked entities and moving money around is simple but has ramifications you need help with.
You can get a small business/startup type accounting firm for ~$2-3k/year at first if all they are doing is quarterly bookings/taxes etc, some will toss in the payroll for 1-2 people at that. Even if you only raised 30k, spend the 3k on an accountant over the next year or you could wind up with a major tax burden or miss out on R&D credits which can help you in the future too etc.
* edit to add this: I'm not trying to sound negative or scare you. Just want to pass along information I have learned and been taught as well. My biggest lesson, being a successful founder means you need to build your advisors team from day 1.