Here are some Power BI trainings I recommend. All these videos deserve to be watched. They will let you grow your knowledge at your own rythm.
Discovering Power BI with videos : https://docs.microsoft.com/en-us/power-bi/desktop-videos
Microsoft guided learning : https://docs.microsoft.com/en-us/power-bi/guided-learning/gettingstarted#step-1
Excellent DAX introduction from Ruth Pozuelo (Curbal) : https://www.youtube.com/watch?v=DwuAypulTLA