Build shower. What slope? What screed thickness?

We had a complete shower (Duschtempel) until 3 days ago, which gave up after 6 years. Now I want to build a shower tray. I know the slope to the drain must be 2%. I want to build a formwork max 5cm high, then lay styrofoam boards in the area and fill the whole thing with screed. Then tile the screed. The drain is in the floor and at the back wall. How thick should the screed be? And how do I best achieve the slope? I am happy to receive tips.
Greetings from Frankfurt, Klaus

Well, now I am totally surprised. I really believed I would get help here. That was probably a mistake. With so many post readers, not a single answer or tip??? Very strange, probably no professionals here after all to help a layman. What a pity

Yesterday the weather was beautiful! The craftsmen will only report this evening! As a retiree, you don’t have to care about that, employees do

Well, now I am really puzzled. I truly believed I would get help here. That was probably a mistake. So many readers of the post and not a single answer or tip??? Very strange, probably no professionals here who help a layman after all. What a pity

Builders help builders.
Life is not a wish concert in a forum ;)

You can also work with a dry screed and a tileable element. It has the advantage that the slope is already built-in, it is also watertight, and has a built-in drain opening - there are plenty of providers.