Pretty much perfect! If you claimed to be Swedish I would believe you.
"Jag studerade svenska på skolan" should be --> Jag studerade svenska i skolan. Think of it as: studiying on school (på skolan), studiying at/in school (i skolan).
I would switch out "trodde" for "tyckte" but it depends on what you mean. Trodde would imply that you think learning Russian would be more important but whilst having no personal opinion on the matter. If you instead use "tyckte", you're still implying that you think that Russian would be more important but you're simultaneously implying that that is your own opinion as well. - Not sure if that made any sense.
"studera ryska språket" needs "det" infront of "ryska". This isn't really necessary in the English language to my knowledge but leaving it out sounds a bit off.
All in all, I'd say you're really good actually! It is somewhat surprising to me that you stopped since you already seem so close to mastering it from a foreign language perspective.