Anyone tried the magnetic device and does it work, thank you,

If you mean the in-line limescale remover, then yes I have installed one in my Hungarian house. I used the electolytic one, not the magnetic one, as I was told the magnetic one doesn't work.
When you read the information on these gadgets you will realise that they can't possibly work, unless you believe in magic - no working parts, no electricity - but they do!
As soon as it was fitted we noticed that there was hardly any lime in the kettle and no scum on the bath water.

Ours was made by Liff and was fitted to the 22mm main water supply. It was put in years ago and appears to be still working efficiently.
Screwfix in UK stock them, but only in 15mm but others may have the larger one. They are also made by other companies besides Liff.

Thank you.