How does the concept of struggle for existence differ from the concept of natural selection?

During natural selection, many species are able to get rid of those weaker than them. And in the struggle for existence, everything depends on how harsh the environment has become, how the species get along with each other, etc.

One of the components of a person's success in our time is receiving modern high-quality education, mastering the knowledge, skills and abilities necessary for life in society. A person today needs to study almost all his life, mastering everything new and new, acquiring the necessary professional qualities.