It is sometimes not easy even just to understand a problem. Andrew Wiles, the Shaw prize winner in mathematics in 2005, proved the famous Fermat's Last Theorem in 1995. He was once thought the proof was done in 1993, but unfortunately a mathematical flaw was found. The flaw was so abstract that even an experienced mathematician would take 3 months to just understand!
Therefore, understanding a problem itself may not be easy, and the only way to overcome it is to keep dwelling on it. Believe it or not, Andrew started dwelling on the Fermat's Last Theorem when he was 10-year-old and he proved it when he was around 42 (after more than 30 years)! Of course, I don’t mean you should stick to a problem for that long. If you have struggled for several days, please seek help from others.