I read (and watch videos) a lot about foreign-language learning. I am convinced that the main useful activity is input: reading and listening, over and over. Teachers call it "comprehensible input". No learning grammar rules. No memorizing vocabulary. No flashcards (or the many apps that imitate them). No testing. No quizzing. No talking to other learners, or talking to native speakers -- that happens later, when talking feels comfortable.
Input can be books, magazines, online articles, Youtube videos, online movies, podcasts. But it has to be stuff you are interested in. Videos you would watch in English. No matter what you do, acquiring Russian takes a long time. If you lose interest, you will stop. If you keep reading/listening, you can't help learning.
At the start, you need to learn the alphabet and any new sounds. Maybe learn a bit about the language. Watch a Langfocus overview video. Read an article or two about its grammar, to get a rough idea. For a while it is hard to find things that are interesting and also simple enough to understand (not perfectly, but to get the main idea). Eventually that will be easy.
I am studying Chinese. I took an online class for a while, but that got boring and I stopped. Nowadays I watch Chinese TV series with English sub-titles. The sub-titles tell me the plot and what people are expressing. The sound tells me how they express it in Chinese. Every minute or two I look up a word or a sentence...but not every word or every sentence. Since I'm retired, I watch one to three hours each day. If I was busy with work or school, I'd have to do more planning, watch less.
I also practice reading every day. I've found several websites with Chinese articles (or stories) at different levels. I faithfully read every day, but only 15-20 minutes. When I read, I look up every word. I understand the sentence. But I don't memorize -- I'll see that word again and again. At some point, I won't need to look it up.
Stay away from books and videos for Russian children. They assume near-fluency in the spoken language, which most kids have by the time they start learning to read.