You get 3 quests to complete at a time. There are around 70 different quest to complete. So there is no need to complete every single one.
Also of note is that the quests in the 2 save slots actually add up. I had 20 in the first and 30 quests done on the second when the trophy unlocked.
This way you can finish it with the easier ones. But most are pretty straightforward, so it should not be too hard in a single slot either.