Luca

Producing sounds versus retrieving words. Naming them as two skills stops people expecting one to fix the other.

The caveat that matters for your specific complaint: shadowing will not fix the words arriving slowly.

You described two problems: pronunciation you cannot hear, and slow retrieval. Shadowing is excellent for the first and does almost nothing for the second, because in shadowing the words are handed to you. You never have to search for anything.

Retrieval improves by retrieving, which means producing language you had to find yourself:

Talk to someone, even badly, even for twenty minutes a week. Nothing substitutes for this.

Talk to yourself if there is nobody available. Narrate what you are doing, describe your day out loud. It feels ridiculous and it works, because the retrieval is real even if the listener is not.

Write, then say it. Writing gives you time to search, and the phrase you had to construct on Monday comes back faster on Thursday.

So run both: shadowing for the mouth and the ear, real output for the retrieval. They are complementary rather than alternatives, and the common mistake is doing only the one that feels productive.

One encouraging thing about your position: understanding well and speaking poorly is a normal and very recoverable stage. The material is in there; it is the retrieval path that has not been built. That is a much better problem than the reverse.