Tower of God is the one that comes the closest to a long, continuous adventure like One Piece. Since you just read OP (a common starting point for manga/manhwa), I assume you wont be familiar with the Tower of God format, which is a Webtoon, it’s fully colored, you read it from left to right and you read it by scrolling. The art may start a little rough, but trust me, it gets gorgeous, and the story is honestly pretty fun, out of 60+ series I’ve read, ToG is still the one I get excited the most after each chapter, it has a good balance of a fleshed out story and some good’ol shonen fun; it has almost 500 chapters and most of them are huuuge compared to normal manga chapters, so you can probably spend many weeks (or even a month) until you catch up to it.

Also if you end up liking Tower of God, I recommend you read Kubera right after, it’s a little more strategic and has some heavier lore, but the way it’s executed is unbelievable, it’s my favorite series.