How do you know if you know enough?

Question

Programming languages

All shalom. There is a very simple and at the same time very complex question. How to understand that you know well Japanese language. Previously, he was engaged in layout, about six months ago he left for the backend. Now I would like to find a job not in the front, but in the backend. but the fear stops me that I don’t know everything and after getting a job I won’t be able to fulfill my direct functions. How to deal with this and actually the second question in the title

Answer 1

stops the fear that I do not know everything

Well then your choice is soap and rope. You will never get rid of the cause of your fear.
Stop whining. Start looking for a job.
When the retirement age comes, then you will know enough. When you don't need to know anymore.