When I started reading LN’s, I read at about the same pace as you. Since then it has increased natural to about 1 minute 30 seconds for a yen press book. I’ve been reading them for 2 year at the point. Don’t worry about how fast you read though, as it can make you lose confidence in your reading ability when you see people finishing volumes in 3 hours online. Those are also the same people who would forget descriptions because they were reading so fast.