To learn Django REST framework properly, first you need to learn python and django to a good level as DRF is built on top of this two. these are free resources. but stackoverflow is not the best place to ask this type of questions.

For learning django and django REST framework, beside their official tutorials and documents https://www.django-rest-framework.org/tutorial/1-serialization/,

I like the varyacademy youtube channel https://www.youtube.com/watch?v=soxd_xdHR0o&list=PLOLrQ9Pn6caw0PjVwymNc64NkUNbZlhFw

Beside Django rest framework, they also provide very good django tutorials as well. including django celery.