My iPad unstable on WiFi and my iPhone wont turn off

Question

After updating both my iPad Air and my iPhone 5s to Ios 8 (yes - bummer) there are more erros than on any version of the Ios than any earlyer version.
My iPad Air has place for a sim Card - but I only use one while travelling outside my current country (Greenland). Since updating I lose WiFi connection every twi minutes or so - each time the dreadfull message "no sim Card" pops up - and then I have to turn off and on WiFi to get connected Again. This is more than annoying - this actually makes it a piece of junk! There are loads of other Things not working - but this one is the game changer - this one turns me to Android.
After updating my iPhone it wont automatically turn off Again. It just keeps on with the turn on screen on - and if I dont notice it - the battery is drained within the next couple of hours. Again - this makes the phone untrustwurthy. I cannot rely on the phone as a primary communication equipment.
These errors are not solved in version 8.0.1 or 8.0.2
I have paid about 2.000 $ and I now have two interesting pieces of JUNK!!!!!!!!!!!!!!!!!!!!!!!

Answer 1

Please tell me that it has NEVER been jailbroke.  If it has not been jailbroke, here are some standard repair procedures:
First, try a system reset.  It cures many ills and it's quick, easy and harmless...
Hold down the on/off switch and the Home button simultaneously until you see the Apple logo.  Ignore the "Slide to power off" text if it appears.  You will not lose any apps, data, music, movies, settings, etc.
If the Reset doesn't work, try a Restore.  Note that it's nowhere near as quick as a Reset.  It could take well over an hour!  Connect via cable to the computer that you use for sync.  From iTunes, select the iPad/iPod and then select the Summary tab.  Follow the on-screen directions for Restore and be sure to say "yes" to the backup.  You will be warned that all data (apps, music, movies, etc.) will be erased but, as the Restore finishes, you will be asked if you wish the contents of the backup to be copied to the iPad/iPod.  Again, say "yes."
At the end of the basic Restore, you will be asked if you wish to sync the iPad/iPod.  As before, say "yes."  Note that that sync selection will disappear and the Restore will end if you do not respond within a reasonable time.  If that happens, only the apps that are part of the IOS will appear on your device.  Corrective action is simple -  choose manual "Sync" from the bottom right of iTunes.
If you're unable to do the Restore (or it doesn't help), go into Recovery Mode per the instructions here.  You WILL lose all of your data (game scores, etc,) but, for the most part, you can redownload apps and music without being charged again.  Also, read this.