It's a bit more complex than that, although I don't yet master the subject.

First thing to know, the simple conversion into FIAT (euro/dollars/yen...) exposes you to paying tax on the feather values.

This is why it is preferable to trade directly with a coin/stablecoin pair.

As for the tax, below a certain annual threshold, no tax. The threshold is around €300 #dyor (Mandatory declaration all the same)

Second point, if the threshold is exceeded you have two options. Either the 30% PFU on capital gains, or according to your tax bracket. It's up to you to choose I think.

Finally, regarding the calculation:

investment: €10,000

profits: 100% or €10,000

profits represent 50% of the capital on the wallet.

So:

Withdrawal * 50% * 30%

for €1,000 withdrawn,

1,000/2*0.3=€150

for €10,000

10,000/2*0.3=1,500

Note, if I am not mistaken, that the calculation of profits is carried out on the entire portfolio and not just the trading pair on which you want to withdraw your assets.

It is implied that losses will smooth out performance and vice versa.

In fact, it's a bit more complicated than that, depending on your investor profile (pro or not)

Knowing if you are a pro investor is quite vague, it will depend on the amounts invested, the frequency of trades etc.

Last point, not declaring exposes you to a tax adjustment, if this is the case, they will come looking several years back. Always plan a stock in advance for your end-of-year taxes :)