Legal withdrawal of funds from the sale of cryptocurrencies

Hello everyone,
There are a lot of tips on the Internet on how to cash out the proceeds from the sale of cryptocurrencies.Butfor some reason, none of them is absolutelylegal. I'm not very clear, are all these mechanisms needed in order not to pay the 13% tax, or because such income, in principle, cannot be legally withdrawn? It seems that cryptocurrencies are not prohibited in our country.
Let’s say that $50K from some crypto platform lands in my Sberbank account. Does anyone know what will happen next?
They will most likely ask me about the origin of the funds. I will honestly say that I sold the Bitcoin I bought 5 years ago.
What will happen next? Will the money be blocked/confiscated? Will it be returned to sender? They will say, okay guy, no problem, we, as a tax agent, will withhold 13%, and use the rest to your health?