How to take 5 seconds of a 400 run for girls high school track?

i am in high school and i am running the 400 and 4by4 and also doing javelin and discus. For the 400 i ran it in 71.7 and need around 67 to qualify for FCIACS also for javelin i threw it 69ft and need 6ft to qualify for FCIACS so i need some tips to improve so i can hopefully qualify for those 2 events this would be much appericated.