Try with a custom, simple nginx server file

Dockerfile

@@ -4,6 +4,7 @@ ENV WEBROOT="/webroot/"
 ENV SECRET_KEY="a1b2c3d4e5f6g7h8i9j0k"
 
 COPY entrypoint.sh /
+COPY default.conf /etc/nginx/sites-available/
 
 RUN mkdir ${WEBROOT} && mkdir /storage && chmod +x /entrypoint.sh
 

default.conf

@@ -0,0 +1,27 @@
+server {
+	listen 80;
+	listen [::]:80;
+	
+	server_name _;
+	root /webroot/;
+	
+	client_max_body_size 100m;
+	
+	access_log /dev/stdout;
+	error_log /dev/stdout info;
+	
+	location ~ ^\/([^\/]+)\/([^\/]+)$ {
+		fastcgi_pass	unix:/var/run/php-fpm.sock;
+		fastcgi_param	SCRIPT_FILENAME	$document_root/share_v2.php;
+		fastcgi_param	url_p1 $1;
+		fastcgi_param	url_p2 $2;
+		include		fastcgi_params;
+		fastcgi_intercept_errors on;
+	}
+	location = / {
+		return 404;
+    }
+	location ~* ^\/[^\/]+\.(php|sh|conf)$ {
+		return 404;
+    }
+}