By lessons what do you mean?
I have done a report comparing Qlik Sense to Power BI and Tableau and uploaded to this site. But if a user (as opposed to a developer) has used Power BI they should find learning Qlik Sense very easy after the script and expressions have been all set up. (And a big step up from Power BI from a user friendliness and overall viewpoint).
Likewise a developer for fairly clean data. Learning Qlik script will take some time though for complex cleansing or transforming though
I find the Qlik measure easier to learn and do than DAX. And at least as powerful.