Problems syncing offline

[leogt25]

I have been using Spotify premium for a while and until now didn't have any big problem, but recently I changed my Galaxy S4 for a Galaxy S6 Edge, and since then I've been having problems syncing my collection offline.
Each song is taking about 1 hour to download and I have more than 3k songs in my collection, so waiting 3000 hours to download all the content is not an option. Lol
My WiFi connection is pretty ok, 15Mbps, and I'm running the last version of lollipop 5.0.2