This video mainly tells a boy's love and persistence in dancing since he was a child, and he finally became an excellent jazz dancer through unremitting efforts. In the video, the scene and background music of the boy dancing with his backpack are all in line with your description. The background music is the English song I Believe sung by Korean composer Eom Seung-min.

Please note that there are a lot of dance videos with similar themes on the video sharing platform, so the accuracy of my answer needs further verification.