Hello @hlc8848. Thanks for posting in the Spotify Community!
This definitely doesn't sound like a good experience, but I'm happy to hear you've tried reinstalling it a couple times. This is a great start. Let's look into some things you can try to help resolve your issue.
First, make sure you're running the latest version of iOS from Apple. You can check this by going into the Settings app, then tapping on General, and then tapping on Software Update. Make sure you're running the latest iOS by tapping Check for Updates.
If you're fully up to date, then a complete uninstall and reboot of your iPhone is a good idea before reinstalling, just to let the iPhone clear out any residual junk. You could also try a soft reset by holding down both the Power and Home buttons for about 10 seconds to forceably soft-crash iOS and reboot it.
Note: you shouldn't lose any data doing a soft-reset, so it's generally safe to try.
If this doesn't work for you, please let us know what iOS device you have by copying and pasting the template below, replacing the sample info with your own. I can then rope in another Rock Star Community Member who is more knowledgeable with your particular issue. Also let us know when the app is crashing: immediately after opening? After logging in? After trying to save songs offline?
Model: iPhone 6S Plus / iPad Pro 9.7 Inch
iOS Version: 9.3.1 / 10.1
This information should be found in Settings > General > About on all iOS devices.