Points got deducted unnecessarily in the May long challenge

Well, I am a beginner, so I recently started grinding my CP skills and learning slowly, I was motivated by the ranking system on here, but in my recent tournament, I scored 300 points hoping to be a 2-star coder after that but instead, I got my points deducted. I solved questions that I could solve, nothing like plagiarism was involved as I solved the questions myself. I am new to code-chef so I am quite uncertain that do we need to solve all questions to advance? if we don’t solve all of them will the points be deducted? I would appreciate if anyone answers, thanks in advance.