Can anyone share me a good GATK4 workflow, I Couldnt find anything good that explanins the process in a crisp and easy way.
If you're looking for a streamlined yet comprehensive explanation of GATK4 and the main Best Practices workflows, you may be interested in the O'Reilly book I co-authored called Genomics in the Cloud. (The cloud part is secondary, all the GATK-focused explanations are applicable pretty much regardless of where you will run the workflows). 

See https://oreil.ly/genomics-cloud