Udemy is a very good way to learn new skills. I think that the most important thing that you have to be able to do as well is ensure that if you are using courses like this to learn animation that you then make use of the courses that correspond with your software that you want to use in it so that you get maximum benefit from it as well. There are many animation software and choosing a course that focuses on another software may not be very helpful to you. But Udemy is a good place to start.You can search on Google there are several platform that provides such services, I will recommend udemy they are very effective, you will also get a certificate at the end of the course.