If you can date american girl, then your level of english is fluent. If you have american friends, then your level is working level proficient. If you feel comfortable talking to Indian colleagues, your level is upper-intermediate. If american university professor doesn’t ask you to repeat your question, then your level is advanced.
I have been considering signing up for their courses. From their website it seems like they use english as the instruction language, is it true? Thing is I don’t know Ukrainian.