Hello LittleGull. Thank you for reaching out. We're sorry to hear you're experiencing these difficulties. We would be happy to help though.
Please go to Menu>Settings>Application manager>All>Phone. From here you should be able to clear the cache - please do so. Then, pull the battery from your device for a full 2 minutes before replacing and rebooting.
In regard to your Wi-Fi connection issue. I recommend completely forgetting the Wi-Fi network you're having trouble with, and then readding and attempting to connect.
If you are still having problems after performing these steps, please reach back out to us on one of our social support channels.
Live Chat Support: http://goo.gl/ZALJm
Thanks, and have a great day!