Hello Zazass,
You keep the soil waaay to wet and for that reason the roots are suffocating due the lack of oxygen in the soil.
Let the soil dry out and water from the bottom in this small pot. Just place the pot in a bowl with 2 inches (5 cm) water for a few seconds. When you transplant the plant you only want to water from at least 5 inches away from the plant to prevent the roots to suffocate again.
Happy Growing Buddy! 💚