Book "Essential PTC Mathcad Prime 3.0" by Brent Maxfield: https://www.elsevier.com/books/essential-ptc-mathcad-prime-30/maxfield/978-0-12-410410-5
You may learn a lot from the help. OK, Mathcad's help sure was better structurized and easier to follow than Prime's help is, but I guess you still can profit by the examples given there. And when I look back how I started with Mathcad a long time ago it was by doing, trial and error, using the help and most importantly reading a lot in the old collab forum. Unfortunately, this forum here is just a poor imitation of it, but it's all we have left and hopefully still is of some use to you.
Furthermore a while ago PTC shared some worksheets for free which may also help you on the way. They withdrawed some of them, asking for money now, but some of them still are freely downloadable from this forum (but hard to find unless you know what to look for, I guess).
Here is the overview page
https://community.ptc.com/t5/PTC-Mathcad/PTC-Mathcad-All-Worksheets/td-p/450684
and here is kind of a tutorial you may find useful
Good luck and free feel to use this forum for asking in case you get stuck.