Q: iphone 4 phones crashes when downloading apps

hi did u try this steps ? If an app you installed unexpectedly quits, stops responding, or won’t open - Apple Support

if the issue persiste try to force restart home bouton and power boutton 10 seconds or try tu restore completly from itunes and set up the device as new How to erase your iOS device and then set it up as a new device or restore it from backups - Apple Support

hi

Try a hard reboot by pressing power/wake button together with home button until apple logo appears in the screen.If the problem not solved,then restore your phone by connecting to iTunes.