Small business regulation - founding year 2025 or 2026

Hello, I'm a student and I also sell used PC hardware (purchase from private classifieds). Business registered in February 2026, but first transactions verifiably as early as December 2025 (PayPal receipts + Excel list available). I already bought several components in December 2025 with the intention of reselling and making a profit, I sold around €1000 in 2025, the rest in 2026. Currently around €35,000 in sales and €9,800 in profit in 2026. All purchases from private individuals. Ke