Software reselling tax related queries

Hi Sir/Madam, Background: ---------------- I [Pvt Ltd] have a software reselling agreement with a US software company who does not have any establishment in India. US company will issue an invoice on my company name with mention of end customer to issue software license. I will be providing Indian rupee based invoice to the end customer and share the license key via digital/email. Questions: -------------- 1. What GST apply while importing software [receiving invoice with electronic software key]? 2. Does any custom/import duties apply? [There is no CD or disk issued, all electronic medium only] 3. Should i withheld the tax while paying to US partner? what is the current rate? [Example, if i am paying 1000 USD, what would be the withheld tax] 4. US company does not have PAN Number, but they are saying they have Form 15D certificate hence could lower the tax. Is this possible, if so what would be the withheld tax rate? 5. Any other taxes apply in the software reselling service? Thanks for your help. Thanks Prakash