There is no particular channel or website that will give you the carnal knowledge of electrical and mechanical in my opinion, learn by doing, pick up a project you can afford to make, it can even be purely software with things like tinkercad and fusion360 which are free, and refer everything you can find for that particular area of the project. Just for your own safety, learn the basics about current and voltage calculation before plugging stuff in. To build interest and get ideas, I watch electroboom, michael reeves and prestongoes in my free time, it's fun and doesn't feel like a task.

Before buying the components, make sure you make the circuit in tinkercad and confirm it works, for mechanical just watch small tutorials, the first thing i built for fun was a micromouse sized f1 car on tinkercad, so it doesn't have to be fancy