This is a polite way of saying that Boaz and Ruth had sexual relations. Many languages have acceptable ways of expressing this. (See: [[rc://en/ta/man/translate/figs-euphemism]])
This phrase probably refers to how Naomi will again experience joy and hope in her life as a result of having a new grandson. AT: "one who bring joy to you again" or "He will make you feel young again" (UDB).
"Seven" was the Hebrew number of completeness. Naomi's sons both died before they produced any offspring, but Ruth bore a grandson to Naomi by Boaz. AT: "better to you than any son." (See: [[rc://en/ta/man/translate/figs-idiom]])