How can I make a Power BI dashboard look professional?

Start with the fundamentals, then build a small project. Once you can explain what you built, why you built it and what the result means, move to a harder project.

For a fresher, projects can demonstrate practical ability. Describe the problem, tools used, steps taken and the result in simple language.

A good approach is to learn one concept at a time and immediately apply it to a small project. Consistent practice is more useful than trying to finish every topic at once.