What should I do to make up for breaking my fast on the Day of Ashura, and can I still obtain its reward and expiate the sins of the year by fasting on the eleventh day?

If someone intended to fast Ashura but did not, then if they abandoned it intentionally, they will not be rewarded. But if it was due to forgetfulness or an excuse like illness, we hope they will be rewarded, for the Prophet, peace and blessings be upon him, said: "When a servant falls ill or travels, the like of what he used to do when he was healthy and resident is written for him." As for someone who was negligent in fasting it, they should strive in the future to seize the reward, and they should frequently fast in the month of Muharram, and increase in repentance and seeking forgiveness.