As usual with these “how long will it take to learn fluent/intermediate/basic/<instert whatever level> and <insert your language of choice> you need to define what is what. With basic conversational russian you will not understand idioms, colloquial russian or hold a conversation about any topic you like. I will define basic conversational russian as being able to talk about everyday things, being able to ask simple questions like where/what/how old and being able to make simple statements. Your vocabularly should be around 1000 words give or take a few houndred vocab. It will cover essential words, so you should know the word for “train station” and “police” but not a less common word like “melancholic”.
The grammar to construct simple sentences and 1000 vocabularly words needed to be considered basic conversational should be achievable in 300-400 hours of study time. Obviously my definition of basic conversational is a tad bit higher than tourist level. It can vary greatly from individual to individual but less than 200 hours of study for mastering the basics seems far fetched even for gifted learners. Keep in mind that russian is a category 4 language(1100 hours to become proficient).
So even if you were to study 10 hours a week it would still take half a year or more to achieve basic level russian. This is the blunt truth, you will not learn anything more than tourist level russian if you spend less than 3 months. Russian grammar and memorizing the vocabularly will take its time. The pronounciation is different matter. You might be able to pick up decent enough pronounciation in a very short time frame or you will struggle for a long time. For most people I would suggest to sign up for a short intensive course instead of trying to self study. If you get the basics down it will be a lot easier to self study down the road, the beginning seems to demotivate people. Also, language schools/courses are good at drilling in routines, if you’re not brigthest student you probably need have your hand held in the beginning. However, I Think formal language education in general has a diminishing return the further you go in your studies, they’re great for beginner levels but so-so for intermediate and advance levels. From intermediate and up you should learn by context and actually using the language through media or speaking to natives rather than just sticking to textbooks.