What is better for junior full-stack developers to practice problem-solving or building real projects? [closed]

Currently, I'm confused about what is better for me as a junior web developer?

• build real projects and learn from them.
• solve problems in HackerRank, LeetCode, etc.
• I'm working and learning (react, angular, node.js) is good to learn more than one framework or get in-depth in one of them then learn a new one.