Final answer:
The sentences contain different types of idioms and their meanings.
Step-by-step explanation:
1. The idiom in this sentence is "live on." It means to manage with a certain amount of money. Example: She can't live on £ 50 a week because her expenses are higher.
2. The idiom in this sentence is "Good grief." It is an expression of surprise or shock. Example: Good grief! I can't believe she lost $1000!
3. The idiom in this sentence is "in the main." It means generally or overall. Example: The food here is quite good in the main, although some dishes are hit or miss.
4. The idiom in this sentence is "find my feet." It means to become familiar or comfortable with a new situation or job. Example: It took me a while to find my feet in the new job, but now I feel more confident.
5. The idiom in this sentence is "absence makes the heart grow fonder." It means that being apart from someone can make you miss and appreciate them more. Example: They say absence makes the heart grow fonder, but I think it depends on the relationship.
I'm afraid that "wars happen" is not an idiom. It is a statement expressing a fact.
Learn more about Idioms in English