tpgifts on "[Theme: Twenty Sixteen] Please help- I can't access my wordpress site"

Hello,
I'm hoping somebody can help me here. I started work on my website and after trying a few themes I found twenty sixteen to the one I wanted to use. Now I can't access my site at all. At first I got a 500 Inteal error message.
I have contacted my hosting company and they have advised the following:

I have enabled WordPress debugging in your wp-config.php
Looking at the error on-screen the problem appears to be with your Twentysixteen theme rather than a server issue:

Parse error: syntax error, unexpected '{' in /var/www/web/wp-content/themes/twentysixteen/inc/template-tags.php on line 251

I am new to wordpress and site building and have absolutely no idea how to fix this :(
If somebody could point me in the right direction I would be most grateful.

Thank you

Sharon

Hello again,
It's ok I managed to work out how to delete the theme from my c panel so I am able to log in now :))

I thought I had resolved this but it seems I haven't :(
I uploaded a new theme and started to customise my site. All seemed to be ok until I opened a new browser to check how it looked. My site is exactly as it was when Twenty Sixteen was installed. If I try to navigate it leaves me with a white screen.
All looks good in my wordpress dashboard and it navigates as it should grrr! This is extremely frustrating lol
Any ideas?