There is the Plugin Handbook. There is also the WP Code Reference.
There is also the thousands of plugins in the WP repository to use as examples for how to do things.
you can try udemy or skillshare. Skillshare is the least expensive if you want to take a lot of courses. If you just want a single course go with udemy because their courses will be more in-depth. Just go there and search for WordPress plugin you will probably get dozens of courses. If the course is more then $19 wait and keep checking back. The price will drop. Right now the courses are $115 or so. Yesterday they were $11. Probably during the 4th of July, it will dope back down to around $11.
Alright great thank you both for the advises!! 🙂
Kind Regards
