lfd for 25km at marathon pace

I did today's duty; a race pace running for 25km around the palace with some Nambanners.
Because of their helps, I could complete a whole distance, but I'm not satisfied with splits.
After half loop run, pace up to 4:30/km for 25km, but pace was a bit slower than I expected.

Hereis the link to view my running log: Intervals (Palace)

It's 42days to go to my next marathon, what should I do the next.
I followed my watch to make splits, I should had to realize the time with my body feeling.
I think shouldn't had to depend on it.