Okay according to Einsteins model of gravity mass/energy can be understood as bending space-time and forming a gravity well. But dark energy supposedly has a negative effect and is actually speeding up the universe, is then to be understood as Dark energy creating something of a gravity hill?
No. Dark Energy behaves normally with relation to gravity. What makes it unusual are three characteristics:
1) It is spread more or less homogenously throughout the Universe. It is for this reason that it may possibly be an intrinsic quality of the fabric of spacetime itself.
2) It makes up 74% of the Known Universe. Of the remainder, 22% is Dark Matter (a completely unrelated concept, despite the similar name), 3.6% is the interstellar gases, and the last 0.4% is everything else (stars, planets, etc).
Combining 1 and 2, you'll find that Dark Energy is not very dense. There's about 10^-29 grams per cubic centimeter. That comes out to just under 11 mg in a volume the size of the Earth. But because it fills all of the "empty" space in the Universe too, that adds up very quickly.
3) It has a negative pressure. Instead of pushing matter away, Dark Energy attracts it, sort of like a vacuum.
Basically, while gravity affects the fabric of spacetime, pressure pushes and pulls matter on top of that fabric. Somewhat counter-intuitively, it is the fact that gravity and pressure are both working "in the same direction", to pull stuff inwards, that casuses expansion to accelerate.
Please do not confuse negative pressure with anti-gravity or repulsion. It is neither.