1. She was at a meeting when I got to her office. the clause that describes the time need to be put at first, then in chinese, it'll be like" when i got to her office, she was at a meeting." To translate "when", You can put "的时候”at the end of the clause. 2. At first, I wrote very slowly. But later, my big brother helped me practice. "at first" can be translated as "一开始“, you can use "但后来“ to express "but later", "但" means "but", ”后来“ means "later" Hope these can help you