If anybody also experiences severe slowdowns in certain areas I highly recommend trying this: link to reddit post. It's just a simple unzip, replace files and rename one file to Game.exe and it runs great now, I tested it myself.
Also, this game is fucking great. Not only does it have interesting H scenes but also writing and story that hook you up while not having tons of boring filler text. The combat is challenging enough to the point that you can't just spam attack but also isn't that complicated to make one have to save every item for a special occasion. The mechanics and overall gameplay are really nice.
I hope this game gets on Steam one day because I would buy it in an instant.