This is the 1208th most frequent Russian word.
изменить
"Изменить" means "to change" or "to alter."
In this sentence, 'изменить' means 'to change' or 'to modify' something, in this case, one's life.
Он решил изменить свою жизнь к лучшему.
He decided to change his life for the better.
Here, 'изменить' is used in the context of being unfaithful to someone in a relationship.
Она изменила своему мужу, что стало для него большим ударом.
She was unfaithful to her husband, which was a big shock for him.
In this case, 'изменить' describes the action of adjusting or modifying settings.