Ich brauche Hilfe...

It looks like overwatering. Or watering with too cold or too hot water... Or watering them in the sun. Watering depends on, pot material, soil (or substitute), RH, Temperature, plant size, plant state (veg, daisy, flower), wind, indoors outdoor,... So to say you need 1,879L or something exact it is impossible. I use cca 1l per watering in 20l pot every 3 days, but i have plastic pots, high RH,... Fellow grower from the previous comment says 3L. if i would water my flowers with 3L they would drown. i am not saying that Jungle_B4RN is wrong, he is right, but for his environment. So you can see it depends where you live and what you use. Probably the best tip i got on the YT. First figure out how much water you need in veg state, start small with 0,3L max per watering and then wait until it goes dry, and then work your way up... Given the size of your plant i would say start somewhere from 0,5-1,l, be sure you wait until soil (lift the pot to weight it) is dry for the next watering... You should aim for 2-3 days watering break in veg, or more some flowers dont need anything for a week or more in veg, so there is no need to water them more. Once you get your water down in veg, lets say it is every 3 days. Then continue with this in the flowering... but monitor how much is she eating, at some point she will eat/drink more. Then if you see she is dry in 2 days, move watering cycle to 2 days. Anyhow happy growing and good luck 💪👊