There a couple of good books:
A modern intro to parallel Fortran programming:
https://www.manning.com/books/modern-fortran
A comprehensive review of all modern and legacy Fortran features:
The Fortran-lang discourse page and Intel Fortran forum are also great for asking questions.
https://www.amazon.com/Modern-Fortran-Explained-Incorporating-Mathematics/dp/0198811896
I have the previous version of this book, which is good.