More information is needed before your question can be answered with any degree of confidence:
1. What tables make up the database?
2. What are each table's columns?
3. How are the tables related?
4. Can a student be trained by only one trainer or by multiple trainers?
5. If a student can be trained by multiple trainers do you wish to aggregate the hours and fees for only the time the student is trained by Christo, or for the total time trained by all trainers? My guess would be the former, but as it stands your
question is ambiguous in this respect.
Ken Sheridan, Stafford, England