How to hide keyboard while dictate text?

Since iPad OS 17 dictating text is a pain because it is incredibly slow. I set up my iPad as a new device and it was fine in the first minutes. When I tap the microphone button the keyboard hides and only an audio waveform is shown. The recognition speed of my dictation is fast as expected then.

But after some minutes, when I dictate another text, this waveform is not shown anymore but the keyboard. Now the recognition speed is again dead slow. The cursor at the text shows a little microphone. When I stop dictation with a tap on the microphone button on the keyboard it takes up to 15 seconds to finish the text. Meanwhile a little blue ring is spinning behind the last word.

How can I get this waveform back and hide the keyboard while I dictate? This is much faster. I need this feature very often but is unusable now.

I have this speed problem only on my iPad 6th gen. but not on my iPhone 12.