What to do against white spots caused by citric acid in wall joints?

I am the man with two left hands. Usually, a new wall is treated with cement residue remover. Unfortunately, I used citric acid for that. That is why the wall has white spots. How can I remove them completely again? I am desperate. I thank you for your support.

Have you already exhausted the mechanical persuasive power?
I have no idea, but I would try:
- mechanically (root brush, wire brush, steam cleaner...)
- in combination with more/stronger acid, if mechanical alone does not work
- possibly with solvent, acetone would be my choice

The second point naturally depends on whether you used too little and therefore only spread it instead of dissolving it, or too much/strong and changed something in the masonry.
Only you can assess that.

To my knowledge, cement residue remover is diluted hydrochloric acid (%?). Lemon is too weak. So it should be the cement visible, not remnants of citric acid. Use the proper acid again and a brush as described above. But once the cement has fully dried, it’s not an easy task...