Can someone please tell me if the way I make quick cash from crypto is dumb?

I started with 600€ total of ethereum and bitcoin about 8 months ago. I use Kraken and live in Germany.

So what I basically do is check the app every so often. Whenever it climbs considerably above 600, say to 650€ or 700€ or even more, I sell 50€ or 100€ or whatever amount of crypto and then withdraw to my bank account to get quick cash. I never withdraw enough to dip below the 600€ euros I originally invested. My account always hovers around this number.

I've made a couple hundred bucks like this and am still below the taxable limit in Germany (600€), but I don't know, I feel like I am doing something wrong? lol Of course I want to make as much money as possible and am willing to start to pay taxes as I make more, but I just love the convenience of just quickly withdrawing the cash and kraken has relatively low trading fees. Idk, any advice would be awesome, I am a beginner! Thank you :]

Alsooo can someone please ELI5 what it means to hold crypto for a year to avoid paying taxes? I bought some bitcoin and ethereum but I've sold pieces of it here and there over the last months. If I want to avoid paying taxes would I essentially not be able to sell anything at all for a year starting with whatever is in my portfolio currently?