I kind of stuck here with a ARIMA estimation. I had a series which I differenced two times in order to make it stationary. The correlogram of the series looks like in the picture. There is one significant spike in the ACF, which I thought would indicate a MA(1) component and there are 3 spikes in the PACF, which could indicate an AR(3). But when I made the estimation of y=c+ar(1)+ar(2)+ar(3)+ma(1), the MA coefficient was not significant at all. I also tried various other combinations, but never got a estimation where all coefficients were significant, they should be, shouldn't they?

Also there are more spikes at the ACF of lag 24 and 25, do I need to take them into account? and if so, how could I do that?

Thanks a lot!