Double Taxation (USA/Hungary)

I am citizen of India. I am working as freelancer in Hungary.

I have some doubts on double taxation especially between Hungary and USA.

Some MNC wishes to hire me as a"contract worker" in USA Payrolls but working for his Client in Hungary forever.

Do i still need to pay taxes like VAT, Corporate tax etc in Hungary as well?

Where can i find double taxation regulation of Hungary with USA?

When is the tax declaration due period in Hungary?

Thanks for your reply on this.

Regards

Ravi