Your dream is rich with symbolism and emotions, reflecting various aspects of your life and relationships. Here's an interpretation of some of the key elements:

1. The Beautiful Sea and Night Setting: Water often symbolizes emotions and the subconscious. The beautiful sea at night could represent your feelings about the unknown or your emotional state, perhaps a sense of calm amidst uncertainty.
2. Sisters and Family: Your relationship with your sisters is central to the dream. Holding your little sister could signify your protective instincts and the care you feel for her, especially considering her current health situation. Your older sister’s departure may symbolize feelings of abandonment or the need for guidance that you feel is missing in your life.
3. The Classroom and Teachers: The transition to the classroom setting might reflect your desire for knowledge or understanding, particularly in relation to your current challenges. The conflict between the teachers could relate to your feelings of frustration or disappointment when faced with unresolved issues or authority figures in your life.
4. The Golden Sky and Quran: This imagery suggests a spiritual or introspective moment. The open Quran and the writing in Arabic indicate a search for meaning or answers. The reference to Ismael (Ishmael) and unanswered prayers might reflect your own feelings of doubt or questioning regarding your circumstances or the health of your sister.
5. Water on the Ground: Water on the ground in the washing hand room might symbolize emotions that are spilling over or needing cleansing. It could indicate a need to process your feelings or address emotional issues that are present in your life.

Overall, your dream reflects a complex interplay of care, frustration, spiritual questioning, and emotional processing. It might be beneficial to explore your feelings regarding your sister's health, the dynamics within your family, and how you navigate challenges in your life. Journaling or discussing these feelings with someone you trust may provide further clarity and support.