"Ese mensaje fue muy dulce"
So sweet. = Tan dulce.
eres dulce
ricura
You can say "Primer grado es dulce" in Spanish. This phrase captures the idea that first grade is sweet or enjoyable.
There are many sweet messages that you can say to a crush on his birthday. One thing you can say is " I hope you have a magical day."
muy dulce
Ella es dulce.
frijoles dulces.
dulces sueños
There is not exact Spanish equivalent of this. You could say"Mi amorcito" or "Mi corazoncito"
te quiero (Spanish) -> I love you (English)
hola muchacha dulce