Pages on this website will contain example code, in order for this code to work you will have to write the code into Mu and upload it using Mu to the Micro:Bit. DO NOT copy and paste the code from these webpages because they might contain white space that could create errors in Mu. Instead each Micropython tutorial has a compressed ZIP file to accompany it. Download this file, decompress it and load the .py file in MU. Then upload the code to your Micro:bit using Mu.
I do bot provide hex files as this could create problems, instead you need to compile the code and flash to the Micro:Bit. If you preferer you can use an online editor rather than Mu.
Some ZIP files will contain extra examples with more complex code. You do not need to do this for the Arduino examples as Arduino IDE ignores white space.