Hard? I find it quite easy, although I did grow up playing the series.
Best advice: try to have at least one ring at all times. If you get hit, you'll lose them all, so try to grab a few back before they disappear. And I must admit the Sonic series has a strange fondness for including underwater sections (every level bar one in Sonic 3 has water in it! ). You have to jump into the giant bubbles to prevent drowning.