Couple of question around Sprint Planning

After reading the Scrum Guide, I can understand that planning should be split into 2 parts;  

For the first part "What can be done this Sprint", I can understand that the Scrum Team creates the Sprint Goal - but then to create the Sprint Goal, I would assume they should forecast which Product Backlog Items they can work on in the next sprint.. is this correct? The phrasing of the 2nd part seems to suggest this

The second part "How will the chosen work get done", I fully understand that chosen stories will decomposed into "work item" (or Sub Tasks if we're using Jira).