What I meant is that if your capital gains are at most €30,000, you will pay 30% as capital gains tax. Of the portion of your capital gain exceeding that sum, you pay 34%.

Let me illustrate what this means with an example:

You buy one bitcoin and pay €10,000 for it. Later, you sell that one bitcoin for €50,000. Your capital gain was €40,000 the year you sold it. The amount of tax you pay is 0.3€30,000+0.34(€40,000-€30,000) = €9,000 + €3,400 = €12,400.

Of course you can deduct the sum you paid for the security you sold.

But if you sell bitcoins or other cryptocurrency at a loss, those losses cannot be deduced from any other capital gains at all. But if you sell, for example, stock at a loss, that loss can be deduced from your capital gains (including crypto gains).

By "normal tax rate" I assume you mean your income tax rate. Income from work and capital gains are taxed entirely differently.