Thank you for the welcome Spatry,
Are you using cPanel for Web Server administration?
Post Merge: December 09, 2018, 12:14:43 AM
OK, it looks like you are using cpanel.. Login to cPanel, go to Domains, yoru subdomain should be listed there. Note the "Document Root" location for your subdomain. The go back to main menu and go to Subdomains and note the locations, they should be the same and there should be no redirections.
Let me know what you find, but don't change anything!