hi @AnnaFless, this topic could be quite useful for many users.
for a new CFD user, who wants to learn the basics (concepts, ideas, good practises), CFD Online is a great place to start (this was how I started exploring CFD!).
The website has a lot of useful info and also contains links to many other resources. It serves as a quick reference to many CFD questions and also has an active forum.
A good introductory textbook is “An Introduction to Computational Fluid Dynamics” (Addison Wesley Longman) by Versteeg, K and Malalasekera W. It is relatively easy-to-read and covers mainly the finite volume method.
A more advanced textbook is “Numerical Computation of internal and external flows: The fundamentals of Computational Fluid dynamics” (Butterworth-Heinemann) by Charles Hirsch. This book covers many concepts in-depth and also lays importance on some of the advanced mathematics. For someone who wants to study CFD in considerable detail, this book is really useful.
cheers,
Manan,