Can't unlock my phone after changing it to Touch ID?

My friend constantly snoops through my phone so I wanted her to stop.Today I decided to put a passcode on my iPhone so she would stop. She quickly figured it out and unlocked my phone, so I was about to change it when I noticed
"Touch ID". I changed my password to Touch ID and it unlocked, but after locking and unlocking it a few times it stopped working. My phone was locked for 5 minutes. My friend had a previous experience with this when she accidentally locked her brother's phone and she said by shutting down and turning back on the phone, it would unlock it. I shut it down and turned it back on. I tried pressing my finger on the home button again, and my phone was locked for 10 minutes. When the 10 minutes was up and I put my finger on the home button, the message "Touch ID requires your passcode when iPhone restarts" displaying. I typed in my password, which then locked my phone for 15 minutes. I can't access my phone and I have no clue what to do. How can I unlock my phone?

Iphone 7 as cheap as you can find?

I want an iphone 7 but i think the apple price on their store is a bit much. I found a website caleld one digitals that has them for under 550 euro, is this a legit website? And i just want it new and i live in ireland so no american deliveries.