Isopropyl alcohol or GooGone works well for removing adhesive. I have never used GooGone in a phone though.
When trying to remove the adhesive, I would suggest using a q-tip. Pouring alcohol or Googone inside a phone is a super-bad idea. You obviously don’t want to short out anything.
Put alcohol or GooGone on a q-tip and go from there. One thing to note, GooGone has a citrus smell, so if you do decide to use it, make sure you use a q-tip with alcohol afterwards to remove that citrus smell from your device.
Good Luck!