WordPress Internal Server Error

Hi there! I have been trying to log into my boss’s business website that he has had for ages. Whenever I try to log into the admin login page (wp-login.php), the screen goes blank and doesn’t deliver me to the dashboard. I assume this is happening because he likely hasn’t updated WP programs or anything in ages. I myself am incredibly WP-challenged, so any help would be appreciated. (Also, I’m sorry if this is in the wrong category - I almost never use Git or GitHub anymore)

When I try to inspect the page, there’s nothing there. I checked the console and it says: “Failed to load resource: the server responded with a status of 500 (Internal Server Error)”.

Is there a way to bypass this issue? (Also please feel free to explain it to me like I’m an idiot because, in this situation, I definitely am). Thank you so much!