I have few microsoft forms and I am wondering where is the data resides. How do I access these data? If I have anonymous user submitting feedback through these form (external users like the whole world) and submits say pdf or file attachment will it be safe and secure?
Very valid questions. Try to read here on the MS blog: https://techcommunity.microsoft.com/t5/microsoft-forms-blog/microsoft-forms-is-gdpr-compliant/ba-p/251515
It lays out where and how data is stored, who can access it and also covers a good question for how to handle forms owned by leavers (employees leaving the organization).
Hope this can point you in the right direction if this is "safe and secure" enough in you/your organizations specific situation.