Downloading to sd card issues
Ok I'll say this for a hundred time that SD card cannot be used for apps as is, you can do that with apps like APPS2SD or link2sd (you'll need root for that), or if you have phone running android 6.0+ you can adopt sd card so it becames like internal storage but you can't use it with other phones until you format it.

Here is how to do it (it says for galaxy s7 but it works with all phones the same way):
http://www.modaco.com/news/android/heres-how-to-configure-adoptable-storage-on-your-s7-s7-edge-r1632/