Was ist der unterschied zwischen sorgen , kümmern , betreuen , pflegen??
This depends on context mostly.
Sich sorgen means to be full of sorrows, and für jemanden/etwas sorgen is what you do to address those sorrows.
Kümmern is the same, but from the opposite direction. Bekümmern is what someone or something does what makes you sad. Kümmern is what you do to address that problem.
Betreuen means being the custodian to someone (its stem is treu!), e.g. kids on an excursion or legally for persons with mental illnesses. It's often used for general caregiving however.
Pflegen means keeping something neat and tidy. You can pflegen your garden, your car or a relationship. Or simply persons.