Start with the Academy link...
Hi,
this will get you the basics:
https://gettingstarted.mendixcloud.com/link/path/40
and this will get you up to speed:
https://gettingstarted.mendixcloud.com/link/path/38
Enjoy, the trainigs are awesome!
You can find some interesting tutorials in the academy section, but you also could download the Mx modeller and start your own project or you create a new project and use the webmodeller.
You can also download the Company_Expenses app as an example. Very basic but useful to get a feel for microflows etc.