Sollte ich meine Samling düngen?

I would be careful with that; most substrates are adequately fertilized for the first 2-4 weeks, so you should be very cautious before the 2nd week! Young plants burn faster and can't handle much fertilizer yet. Usually, it's enough to start around the 3rd or 4th week or to repot every few weeks. You could add what kind of fertilizer and soil you're using in your report; that would be helpful for questions like this! Best regards and peace!

Not yet, they have a lot of food in the cotyledons. You can start round week 3 or 4. In future water around the sides of the bag and not right down the stem.