First protect people and prevent another collision. Deal with injuries or immediate danger before collecting paperwork; record details only from a safe place.
For an accident record, distinguish observations from assumptions: location, date, vehicles, damage, positions and witnesses. Mark circumstances carefully and read the complete document before signing; do not confirm facts you believe are wrong.
A sketch should clarify road layout, vehicle positions and directions, not invent measurements. If accounts differ, record the disagreement and seek appropriate assistance rather than guessing to finish quickly.