The first mission for Opia focuses on hunting. Essentially you need to beat her by acquiring more pelts than she does within the time limit specified.
Once the mission starts, green investigation zones will appear on the map. We need to run over to these to find prey to hunt. Whilst inside the zones, activate Eagle Vision to have animals appear bright red. When you know where they are, simply shoot them from afar are sneak up and assassinate them before skinning. You can also kill them in one hit by firing a rope dart at them, making for a quick kill.
You will have to repeat this process another 2-3 times, so keep at it! Whilst you hunt, note that Opia is also hunting animals so don’t be surprised if she occasionally runs in and steals your kills from under your nose. If this happens, don’t fret, just head to the next location immediately to get the jump on her.
Once you have killed and skinned enough animals, you will be ambushed by a white jaguar. Quickly hit the on-screen button prompts to shake it off, then pull out your pistol/rope dart and shoot it as it runs away (or chase it down and assassinate it).
Killing the white jaguar will complete the first memory.