comments:
I agree with those who have suggested getting a tutor. I have two other suggestions: (1) While deciding on a tutor, also take at look at this textbook for heritage speakers: Olga Kagan, Russian for Russians, https://www.amazon.com/Russian-Russians-Olga-Kagan/dp/0893573019 It should help you get a better handle on grammar, which will in turn build confidence when speaking. Since you are applying to a Ph.D. program, presumably you have the study skills and discipline to get something out of it even with self-study. (2) Are you able to afford to spend a couple of months in a (largely) Russian-speaking city to immerse yourself? I think you'd be surprised how much you would learn when you absolutely had to speak Russian. For obvious reasons, going to Russia or Belarus might not be the best idea right now, but a couple of months in Almaty, Bishkek, Yerevan, Narva or Daugavpils might really kickstart the language recovery process.