The first is the one I don't know how to explain. Someone said, "Students are easy to find," when what they meant is, "It's easy for students to find." This is the null subject "It" or "There" and if anyone has a good way to teach/learn it, I hope you contact me.
The second is the use of "At first ~." This was used for the first reason of a task 3 conversation summary. The student said, "At first,~" instead of "The first reason ~." The reason this is wrong is that "At first" suggests a contrast, as in:
- At first, I thought she was a nice woman, but then she broke my heart.
- At first, I thought I'd win the race, but then I got really tired.
Please use English well!