Hi@akhtar
There are lots of online courses available in the market that gives online training on Apache Spark. But I took Edureka's online course in which they covered the basics of Hadoop along with Spark. To understand spark concepts, it is required to know some basic concepts of Hadoop.
I suggest you to go through the link given below for more details.
https://www.edureka.co/big-data-and-analytics