US Immigration from Greece

Hello i have so many questions about the passports,the visas,and what i have to do before or when i submit online for n600k.Has anyone Greek did this before so he/she can delight me about the steps i have to take?what kind of visa must have my children so they can travel to the u.s. to take the oath?i must go to the embassy in athens?what should i do first,passports?visas?n600k?im so confused.

Hello when i apply online for N600K and i have to upload certificates,i must upload the translated or both greek and translated certificates?

Hello greek birth certificates for chidren must have apostolite sign.the certificate and the apostolite sign are two pages.they must be at different pages or in one page both sides for n600k online?

Hello i would like to ask if my childs birth certificates translation from Greek to English have an expiration time?

I am applying for a spouse visa outside of the US. My case has just been transferred to NVC yesterday. The next step is paying to NVC but I wanted to delay a few months for the process. Basically, I want to aim to be interviewed half a year from now or later. Also, collecting my police record from my birth country will take a few months since I am living in a third country (where I applied for the final interview appointment). So, I was thinking of taking extra time to pay NVC fees and submitting financial documents so that the whole process takes longer than usual. I was wondering if there is a deadline to pay NVC. How long can I wait to pay the NVC fee? If payment has to be done soon, can I wait to submit financial documents? How long can I take time to submit these?