1: 你好吗?

Read as 'ni hao ma'.

The meaning is equivalent to 'How are you'.

The first character, 你(ni) means 'You'

The second character, 好(hao) means 'Good'

The third character,  吗(ma) is used to end a sentence in question form.

This sentence literally mean 'You good?' or 'You fine?'

It is used to greet each other.

2: 我很好

Read as 'wo hen hao'

This means 'I am very good'.

The first character, 我(wo) means 'I'

The second character, 很(hen) means 'Very'

The third character,  好(hao) means 'Good'. Same as the one in the first sentence.

3: 谢谢

Read as 'shea shea'

This means 'Thank you'