Do not count your chickens before they hatch means don’t make plans assuming things will happen a certain way – wait to see what happens first.
For instance: It’s not your birthday yet, so don’t count your chickens before they hatch.
What is chicken and egg situation: when it is almost impossible to say which of two things happened first, or which is the cause of the other.
For example: I seems it is hard to find a job without experience, but how to experience if you don’t give a job. It is a chicken and egg situation.
Practise your sentences in the comments.