I went to the north side of mana ruins but there's a farm that I cannot reach, please give me a process thank you!!!

Hello.

I'm not very good at explanations, so please bare with me.

When you reach that end of the Mana Ruins, you will see the gathering point on the other side of the wall. Keep walking up until you see a barrel and just before that, a pillar. Jump up on to the pillar and hop onto the other one. There is a small spot to dig for veggies and a small monster. Kill the monster, and continue walking past where it was standing. You will see another barrel and an item pouch. Continue walking past that barrel and you will be behind a wall. When you can no longer walk in that direction, proceed forward. (Push the down button on the control pad or thumb stick.) You will be on the other side of those rocks that appeared inaccessible.

Sorry for the long explanation, but I hope this helps.