I do not speak Korean?

You can get around Korea very comfortably with zero Korean, especially in the cities. For subways and buses, install Naver Map or KakaoMap, which are the local standards and far more accurate here than Google Maps, and both have English interfaces that give exact routes, transfer points, and fares. Get a T-money card from any convenience store, top it up with cash, and just tap on and off; it works on subways, city buses, and even taxis nationwide. Subway stations have English signage and announcements, and the lines are color-coded and numbered, so they are easy to follow.

For taxis, use the Kakao T app: you set your destination on the map so you never have to pronounce an address, you see the fare estimate up front, and you can pay by a registered card automatically. If you flag one on the street, just show the destination on your phone screen. For intercity travel, the Korail and SRT apps book KTX tickets in English, and the Kobus app handles express buses. Papago is a great translation app for any on-the-spot conversation, since its Korean is better than most. Honestly, between Kakao T, Naver Map, and a T-money card, most foreigners travel the whole country without speaking a word.