I disagree with your assessment. But, of course, just as I'm entitled to my own opinion on the matter, you are also entitled to your own.
As with almost every story ever created, pacing changes at different points, depending on the feel of the scene. When the MC was initially in hell, it felt pretty slow to me despite the MC killing his captor and becoming the next ruler of the kingdom. The place being attacked and conquered was fast-paced, which felt correct to me, including the time directly following, when the MC taught his enemies a lesson. Then, because there was no need for continued action pacing (warring between factions was over), things slowed down considerably. This is what I would expect in any novel, play, or short story. To me, then, the pacing was fine: nothing felt too rushed or too slow to me at the points where things changed.
It's been some time now, but I don't remember ever thinking the English was terrible. I would say it could definitely use some proofreading, but no more so than a lot of games on F95.