Q: upload button not working when using  shareit app in iphone 6

Hi surabhi90,

I see that you seem to be experiencing an issue with one of the apps on your iPhone. Here is an article with some troubleshooting suggestions that should be able to help you address this issue:

If an app you installed unexpectedly quits, stops responding, or won’t open - Apple Support

https://support.apple.com/en-us/HT201398

Thanks for using the Apple Support Communities. Have a good one!