Yes, it does depend on how long you hold in Germany. This is the rule for private people):

If you hold your Bitcoin for more than 1 year, no tax at all on the profit.

If you sell or spend your Bitcoin within 1 year, the profit is fully taxable under your personal income tax rate

That rate depends on your total income — it can be anywhere between 14% and 45%.

There's a small tax-free allowance of 1k per year for these kinds of sales.

Say, if you buy BTC at 2k and spend it at 2.5k (within 12 months), you technically owe tax on the 500 profit unless it's your only transaction that year and under the 1k limit.

Insane