I can't download or update apps from the app store why?

Impossible to say from what you've posted. What happens when you try to download them ? Are you getting an error message ? What have you tried to see if it fixes whatever the problem is ?

My phone came up lost mode I lost everything . Now all my apps won't come back please help

What do you mean by 'wont come back' ? Do they show in the Purchased tab in the App Store app on your phone for redownloading ?