How can I calculate Ampere Per Hour if Intensity has been given
Ah means ampere-hour, not ampere per hour (otherwise the battery would last forever).

But your calculation is correct, the battery has enough capacity for delivering 2.15 ampere (for one hour), so if your robot uses 1.8 A, it lasts for  2.15 Ah / 1.8 A = 1.19 hours, which is 1.19 * 60 = 71.6 minutes.