Sounds like the problem I am having ( creating my first html to wordpress theme) , and I’ll have to figure out the code that is causing the problems.
But there are two ways to access your site (actually even more I am sure). First make sure you have a backup pf your theme you are customizing locally. Download via FTP if not.
You can delete the theme that is giving you trouble via FTP and it defaults to one of the Twenty themes to give you admin access, at which point you can change to a working theme for the time being while you check your code of the theme giving you trouble.
Or, what I do sometimes is say the theme you were changing the code and causing you trouble now is named Memphis, either download a working theme via FTP or I usually have backups laying around, say like twentyfiftheen , and I will rename the twentyfiftheen working theme Memphis and upload it via FTP to get admin access. The first way is the easiest but this works for me too. I have done both and they worked for me.
I am with you and having issue’s learning and changing code too.
Good luck!
