Hola Samantha
The difference between "yo aprendo arte hoy" and "estoy aprendiendo arte hoy" is in how they express the timing of the action.
"Yo aprendo arte hoy" uses the simple present tense, suggesting either a habitual action or a scheduled event for today. On the other hand, "estoy aprendiendo arte hoy" uses the present continuous tense, highlighting that the action of learning art is currently taking place or is ongoing today. The continuous form focuses more on the immediacy and ongoing nature of the action.
I hope you find this explanation useful!
Feliz semana
Silvia