Moses continues to speak to the Israelites as if they were one man, so the words "you" and "your" here are singular. (See: [[rc://en/ta/man/translate/figs-you]])
Here "heart" refers to the whole person. This can be stated in active form. AT: "if you stop being loyal to God ... and the people living in the land convince you to bow down and worship other gods" (See: [[rc://en/ta/man/translate/figs-synecdoche]] and [[rc://en/ta/man/translate/figs-activepassive]])
# to you today that you ... you will not prolong your days
Moses speaks to the Israelites as a group. (See: [[rc://en/ta/man/translate/figs-you]])