I'm interested in various Slavic languages (Polish, Serbian, etc.) and was told to start with Russian to not only learn a useful language but a gateway language to other West, South, and east Slavic languages.

Hello,

I'm a fairly competent speaker of Russian, and I want to learn at least the basics of one or two other Slavic languages, but I'm not sure which. Could anyone give me their recommendations? Please state why you recommend said language.

Thank you!

My dad is from Poland and I want to learn a language that would help me in learning Polish from him.
Would Russian be helpful because they are both Slavic languages?

I kind of want to learn Russian but I might be overlooking other Slavic languages?
I really need some help because I need a language I can stick with...
Thanks!

I'm an American, and I took Russian for a while in college, but no Polish.
Since Poland was Communist for many years, and also because it's another Slavic languages, will most Poles be able to speak and understand Russian, too?