can i have banana after attham?

Yes, banana can generally be taken after attham when you break the fast, if it is allowed in your family or sampradāya tradition.

A few Jain-friendly points:

• Take parna in a proper, शांत and respectful way.
• Prefer simple, sattvik, and light food first.
• If your tradition says to begin with water, fruit, or light food, banana is usually considered acceptable.
• If you follow a specific guru, upashray, or sangh rule, please follow that guidance.

So, in general: yes — but tradition-based rules should be followed.