1. “The cashier is on checkout” → “The cashier is at the checkout”: Use “at” for locations like checkout counters. 2. “She sells clothes what does she sell?” → “She sells clothes. What does she sell?”: The question “What does she sell?” should be a separate sentence. 3. “What is in his hand?”: This sentence is correct. 4. “How to spell” → “How do you spell…?”: In questions, use “How do you spell…?” 5. “He is repairing the light”: This is fine. The structure is correct. Would you like to practice more with these types of sentences? Book a conversation lesson with me to refine your skills!