What is shadowing
Shadowing is a repetition of a phrase almost simultaneously with the audio. You don't listen to individual words, but to the tempo, stress, pauses and connections of sounds.
The technique is useful for automating already familiar structures. It is not a substitute for understanding and should not be the first step for completely unfamiliar text.
How to exercise safely
Take a short recording of 10–20 seconds. Listen to it first with the text, then repeat it slowly, and only then try speaking along with the audio.
Record one take and compare not everything at once, but one parameter: for example, the emphasis in keywords or the length of pauses.
What to avoid
Don't chase the speed of the carrier and don't judge yourself based on one sentence. It is more important that speech becomes clearer and more stable.
If sound regularly interferes with understanding, move it into a separate exercise and return to shadowing after that.