Hello everyone

I was visiting my brother in swiss on a tourism Schengen visa .I was a student and I don’t work .however ,during my visit I did withdraw money from my fx account .however my brother received a mail mentioning that I have pay around 7000 as taxable income from investment
I did pay the whole amount

However ,I was told that I can get back the amount as I don’t reside in swiss nor I do work here

Can someone tell me the process and what is the procedure o get back the money and how long does it take

Thanks in advance