u/Calm_TeaLeaf

I am going to Istanbul this summer on a solo trip for my senior year, and plan on going westward after spending some time in turkey. What is the best way to go about exploring Eastern Europe, especially North Macedonia, Montenegro, and Bulgaria, using train lines and the such, im assuming. I also need to find a way to get back to Istanbul as well for my flight out, so maybe some sort of circle around Eastern Europe is the best play? I have 27 days. Any help is so very appreciated, I am new to traveling solo.