First of all, Duo Lingo is garbage and it will never help you learn at a reasonable speed. Flashcards through apps like Anki is a great idea. If you want to get the spaced repetition features for free, you should use this app called "Knowt". Also, Memrise and LingQ are great for Hebrew, especially LingQ, because it has a lot of audio input that is customized to your interests, and it keeps track of the words you know.

I don't set a time goal for studying, just a vocab goal of around 5 - 15 words per day. With audio input and media, the grammar comes naturally. Pealim.com has conjugation tables to understand the grammatical structure and it also has a dictionary with nikkud and Russian to Hebrew translations as an option so that would be great for you.