A new lease on life (or in British English ... of life) is when you recover health and activity. It might be used of a person who has, for example had hip replacement surgery. Or it might be used when someone takes up a new active hobby.
When Jason retired he became rather depressed and lonely, but joining the golf club has given him a new lease on life. Now he plays several times each week and he has made lots of new friends.
It can also be used of things when they are repaired, or re-invigorated, allowing them to be used for longer.
Upgrading the RAM gave my computer a new lease on life.
It is found in dictionaries: Eg Cambridge
The metaphor is from a lease on a house, which is a agreement to allow someone to live in a house for a certain amount of time. When the lease runs out you may be able to get a new lease, to allow you to live in the house for longer.
The lease on the house runs out in 2025 but you can take out a new lease from the landowner when that happens.