Give me a list of descriptions of the problems that are reported by the staff whose first name is Christop.
create table staff (staff_id varchar, staff_first_name varchar, PRIMARY KEY (staff_id)); create table problems (problem_description varchar, reported_by_staff_id varchar, PRIMARY KEY (problem_description))
select t1.problem_description from problems as t1 join staff as t2 on t1.reported_by_staff_id = t2.staff_id where t2.staff_first_name = "christop"