1. "нашла" is only used when you are physically looking for something and found it. The past passive has nothing to do with this sentence. If it were me I would say,
Я думаю (поняла) что самый лучший путь ..... but that loses some of the meaning of the original sentence.
A better alternative would be to use
"выводить" that means something like infer, or conclude which is much closer that think/understand in the previous sentence. But I am not sure exactly how a sentence can be formed with that verb. So a more 'everyday' russian speaker is needed here
2.
Иногда музыка выражает мысли/чувства лучше чем я когда либо могла. The words
things/stuff are very common in english but
вещи(вещь)/штуки(штука) are not all that common in russian. So it is better to be more detailed
Hope this helps
P.S. I don't know what dictionary you are using but
http://www.rambler.ru/dict/ works great for me