Hey symphonic! I've played both of Debussy's arabesques, they're wonderful pieces, this second one is actually pretty difficult, especially when it's live, I've found any nervousness I have stiffens up my arm and I botch all the little ornaments. It's actually very difficult, no matter what ABRSM says!Anyway, on bar 5, smoothly roll the chord with a little bit of pedal, maybe 1/3 to 1/2 of the way down. Not so much to where you cannot play the fourth note of the right hand hand stacatto, but not so little that the chord dies out too fast.If you want to get better at those trills, just play the trills (not the bottom note) with the correct fingers. Very slowly at first, then work your way up to speed. Then try putting the last note with it, but leave out the first one. It will sort of sound like a horse galloping.Good luck with this piece, you won't regret playing it, if you can play it well. < Fortunately, we have a recording of Debussy himself playing it. Listen to how he plays those large chords.