Where to learn MDX

Hello everyone.

Could somebody please give me some hints on where to learn about MDX.

Mostly I am interested in stuff like "MDX Query - The Basic Query" like mentioned on following microsoft forum (https://docs.microsoft.com/en-us/sql/analysis-services/multidimensional-models/mdx/mdx-query-the-basic-query?view=sql-server-2017)

Are there EDX or LinkedIn-Learning classes or similar that somebody can recomend where this is covered ?