When you say "fast paced sliders" do you mean the that the sliders are fast throughout the song or the song just has randomly fast sliders? If it's the former, then you just have to practice but if it's the latter, you'd have to memorize those sliders in the song. Your second problem is probably just miss interpretation of the song since you really only should be getting 50s if that's the case. Try playing with hidden, it helps with figuring out the beat and you'll probably see less 50s.