Hi Leonardo, for goal visualization I don’t have any clear advice. If you search on those two keywords you’ll find a lot of interesting techniques. For me some sort of day dreaming works fine, imaging what would be the perfect end situation. One of my favorite quotes on this: “it’s better to aim too high and miss than to aim too low and hit your target”.
For goal setting you could find inspiration in OKRs (Objectives and Key Results). For splitting goals into actions you could lookup Work Breakdown Structure as a technique. It also resembles the Scrum activity “refinement” where you focus on defining next activities (stories) that would bring the most value. More details can be found in the Scrum Guide. There are also plenty of good articles out there on this topic including how to split stories into smaller ones.
Hope these pointers are helpful. The best advice I can give is to just get started and experiment with whatever technique or tool you think could work, then adapt based on the new experience. And have fun of course. Good luck!