Aight,
1st, might be unstable connection, make sure wifi is running in good condition
2nd, "app not installed" could mean you need to free up some space (a lot, preferrably)
3rd, either there's another copy of the app, or your phone isn't compatible with the build. You can find videos on how to fix the "parsing error" part.
Hope this helps, but I'm not quite sure with myself ; w;