enabled multisite -- but I think I just broke my site?

I followed these instructions: https://premium.wpmudev.org/blog/ultimate-guide-multisite/?utm_expid=3606929-72.AqocGS0YR5Gn_p3r6t6_AA.0&utm_referrer=https%3A%2F%2Fwww.google.com.au%2F

My home page appears to be fine- but when I go to click a link on there - it just comes up with an error.

I tried editing via upfront -- but doesnt load- it just suspends there

please help