5G poses a major architectural and functional change of a network. This move brings along many security questions and many have been tackled for the non-standalone or standalone architecture. We will discuss how to get securely from a 4G or non-standalone architecture to a standalone architecture. Different migration scenarios and architectures are described and what are the specific security aspects of it. This will be put into context with latest GSMA and 3GPP security approaches and features. Additionally, as we gain experience from the initial deployment and collect open issues related to standardization, operation, and implementation, we aim to provide an overview of practical guidelines and recommendations for mobile operators for the implementation of 5G networks.