Is Lynked.World secure? How do we know that our documents will be safe on Lynked.World blockchain?
Documents won't be stored on blockchain as Lynked.World is on ETH blockchain. They will be stored in the application.
How do we know that app will be safe and that our documents won't be hacked in the app? Is there some mechanism to prevent that and who is guaranteeing the safety of our data?
You should always back up your own data,no matter what kind of security measures there are.You can use Google drive or something else.