Adding a second router?

I built an ADU (office separate from our house). I ran ethernet cable to the office which works great. However, because I hard wire my computer to the ethernet I have no wifi (it's too far from the house, even with the wifi pods I bought). Question is, can I buy a 2nd router, plug it into the ethernet in my office and have wifi, in addition to hardwiring my computer into the ethernet?
Would this be on the same wife network as my home? And if so, could I create a mesh network for my yard, office and house?