Welcome! You are taking the first steps toward a really fun hobby!
Maybe I missed it, but is this a preformed pond or is it a liner? Either way, kinda small for more than just a few goldfish, so plan accordingly. As others have said, read as much as you can: learn, learn, learn! Never stop learning
Also, if you keep fish, get a water test kit -- an absolute essential! The smaller your pond, the harder you'll need to work at keeping the water in good balance.
Yes, you want your pump at the opposite side from when your filter flows back into the pond. That keeps the water moving & circulating throughout the entire pond instead of just in a small spot.
If you put your pump on the
bottom of the pond, and something happens that drains your pond (been there--done that), you lose everything (if you have fish). Pond will/can completely empty. There is no "rule" that says how deep to sink the pump, but if you have a small pond, look at it and decide how much water will save your fish.