The Sabbath began on Friday at sunset and ended Saturday and sunset. The day after the Sabbath was the first day of the week. This day began on Saturday at sunset and ended on Sunday at sunset.
Jesus wanted the disciples to make other disciples. That is, he wanted them to tell people about Jesus and help them to believe in Jesus and to do things that honored God. They did this by going to different places, baptizing people who believed in Jesus, and teaching them how to live in a way that honored God.
Jesus said that he would be with the disciples until the end of the age. Some scholars think Jesus would remain with them for a time on the earth after he was resurrected. He will help them to do the things he wanted them to do. Other scholars think Jesus wanted to say that he would be with every generation of Christians to help them do the things he wanted them to do.