Reincarnation
Thankfully, whatever method was used to make the portal, it allows you to be reincarnated as someone who fits your criteria. You shall have all their memories and skills, you'll be able to act just like they did. You can decide how far you merge, if it's just your mind in their body with their memories and skills, or if your personalities merge completely. If you want you can decide how this works if you want to figure out a way to make this not stealing someone's body, mind, and soul from them.