I can’t copy and paste on my iPhone 6s Plus

Greetings lettie112,

Force the app to quit, restart your iPhone, and ensure iOS is updated. If you're using a 3rd party app, test after deleting and redownloading the app. You can see those suggestions outlined in the article below:

If an app on your iPhone or iPad stops responding, closes unexpectedly, or won’t open - Apple Support

Kind regards.