Hi @Dmitry - this is a great question, and such an important topic when recreating in the backcountry!
There are two resources that I would recommend looking into:
1. The American Avalanche Association - On the "education" section of their web site, you can find lots of online resources, as well as find in-person courses in your area. This website is also a great resource for locating your local avalanche center and finding current and future avalanche forecasts.
2. The American Institute for Avalanche Research and Education (AIARE) - In the "Resources" section you will find some great videos and tutorials. This website is also a great resources for finding high-quality in-person avalanche education in your area.
And as you stated in your post, online resources are a wonderful starting point, but in-person avalanche instruction is the best way to learn, fine-tune your skills, AND stay safe.
I hope this helps! Stay safe and happy trails!