Having issues with OnTriggerEnter & Exit

Please help, I am having an issue with OnTriggerEnter & Exit and its probably unity2017.

error reads [Feature ‘local functions’ is not available in C# 4. Please use language version 7 or greater.]

I was unsure of which version of unity to install, so went with the most current, also using visual studio 2017 commnity for mac. Everything as been working so far as I go through the book until I got to page 159.

I searched online for the error and what c# 7 has in place of OnTriggerEnter & Exit and could not find an answer or a solution that worked. I did come across onCollisionEnter but that resulted in the same error.

What shall I use? Is it something that needs updating or do I need to uninstall unity2017 and install unity 5.x?

Thanks for your time

oh my goodness,

please disregard question as I put code snippets in Update ( ) and not below it. Over an hour of my life I won’t get back and a headache to resolve now =)

Best Regards,