fakruzaruret Flarum has dropped the use of api.php and admin.php. You can remove those location rules.
Please check the date of the resources you consult to install Flarum, a lot changed in those few years. The official install instructions should be all you need. Guides for beta 7 are outdated. Guides for 8/9/10 might still apply to the current version.
If his is still the same installation attempt, please please stick to a single discussion and not dig up every discussion about ngninx we have from 3 years ago. Thanks! Having all your attempts and issue in a single discussion will greatly help our ability to follow where you are stuck.