Can someone suggest me some courses for becoming a firmware engineer.

So, I am a senior full-stack web developer, and I wanted to spread myself a bit and wanted to get into firmware development. Even though my primary "focus" has been web development, I do know some languages that are used for things other than just web development, like C++, C#, C, and Java. I know a bit about some C++ frameworks like QT, I provided that information, as I thought that it could be relevant. If you're interested in knowing about what my "knowledge" about web development is, or about how experienced I am, then just either DM me or ask about it in the comments. Have a good day!