Maybe I'm an idiot but I don't know how to get the top off of my

The cistern lid is held down by the chrome assembly (which includes the two buttons that you press to make the toilet flush) sticking up in the middle of the lid. You need to unscrew that (anticlockwise) to be able to lift the lid off, to get to the inlet valve, etc.

If the water is running in very slowly, chances are high that the small screen filter under the inlet valve is partially blocked. Working inside the cistern, you need to unscrew the inlet valve assembly (noting the order in which the various parts come out!), then unscrew the cranked fitting just under that, to get the screen/filter.

Hi,
If yours is like mine, which has the flush and half flush that make up a circle, do the following:
Press either the flush or half flush.
Lift up the other half. (It should come straight out)
Lift up the remaining half.
There should be a white plastic screw that you can then remove.

Hope this helps.

Duravit happ d cistern - after flushing i can hear a noise like air leaking. i have taken off the lid and lightly pushing the assembly inside fixes it. any ideas what is causing this and how to fix?

thanks

Will it pull up on any side? There may be something catching it. Point a flashlight in between the top and tank. You may be able to see if it is attached. There should be some play in there as you try to raise it up.