To meet the requirement of routing cases based on language proficiency and knowledge area, Omni-Channel Skills-based Routing is the best solution. Skills-based routing allows cases to be directed to agents who possess the specific skills required to handle the case, such as language fluency and product expertise, ensuring efficient and effective case resolution.

Visual Workflow is a tool that allows you to create flows that automate business processes in Salesforce. Flows consist of elements that define the logic, data manipulation, and user interface of the flow. Elements can be used to pass data to legacy systems using outbound messages or Apex actions, update fields in the database using record elements, and perform other tasks. Only one version of a flow can be activated at a time, meaning that only one version can run when triggered by users or processes. Verified Reference: [Salesforce Help: Visual Workflow]

Salesforce allows Knowledge articles suggested by Einstein to be attached to customer emails as part of standard Case Management capabilities. Einstein's AI-driven recommendations help agents by surfacing relevant Knowledge articles based on the case context, which can then be shared with customers to provide self-service options or additional information. This feature not only enhances the efficiency of case resolution by equipping customers with helpful resources but also leverages the power of AI to improve the relevance and personalization of customer communications, thereby enriching the overall service experience.