Good day, please we are set to start using the addon (DragonByte eCommerce) allowing users of our forum to list products on our forum platform. But need helps in setting up the store

The above is the error we are having each time we try to approve product on our platform
e.g. 1: When user create product, the we try to approve it as admins, when we try to approve the product, we are having errors. See code ( Oops! We ran into some problems. ''Security error occurred. Please press back, refresh the page, and try again. )
Please how do we resolve this error and start approving products listing for public views on our platform?
2: What is the best feature picture size for ( DragonByte eCommerce ) so we can adapt
3: Is there ways we can use multiple currencies when people want to make a purchase?
4: If there is a walk-through guide or video training for working with ""DragonByte eCommerce"" we will love to have it
Thanks and that is all for now

The above is the error we are having each time we try to approve product on our platform
e.g. 1: When user create product, the we try to approve it as admins, when we try to approve the product, we are having errors. See code ( Oops! We ran into some problems. ''Security error occurred. Please press back, refresh the page, and try again. )
Please how do we resolve this error and start approving products listing for public views on our platform?
2: What is the best feature picture size for ( DragonByte eCommerce ) so we can adapt
3: Is there ways we can use multiple currencies when people want to make a purchase?
4: If there is a walk-through guide or video training for working with ""DragonByte eCommerce"" we will love to have it
Thanks and that is all for now