Hi Michael, welcome to Mendix! Lots of programmers have made this move, me included. First thing i would advise is to take the learning path for Rapid developer at https://gettingstarted.mendixcloud.com. This is not having hickups and tell you all you need to know. Do all of them and take the Rapid Developer test. With some effort you will be able to pass that test in a week or so. Keep going with the learning path for the Advanced Developer and you might consider taking a three day course. And just keep at it by creating stuff.
But to answer your question; If there are any videos not working, then you best raise a question at support.mendix.com They will look into it and repair them.
Please check this link https://gettingstarted.mendixcloud.com/link/path/38 for the Rapid Developer Learning path