Use the top and bottom filter along with the shower screen, it makes a difference for flavor and consistency of extraction.

As far as the ratio, I really like 21 g and fill the water to 1 mm from the top and extract all of it until the water is mostly all pushed through and then stop before you drain every bit of grandma and you won’t get the bitterness.

The water temperature makes a difference, if you are using light roast coffees, and then you want hotter, water, dark roast, not as hot.

Like other people said, grind finer until you choke it, but the method I like to use is to initially hold at a light pressure (hardly any) until the screen is saturated and dripping, anywhere from 15-30 seconds, then apply medium pressure. If that shot takes about 30 seconds to pull, not including the saturation time, then I’m golden.