I have wordpress site. since last month, everyday 2 files generated automatically and, index.php edited with some base64 code which causes open few page, if anyone open my site.
When I deleted these files and base64 code from my site, site works fine. and these file generation happens twice daily.
Your server might be hacked/compromised. One thing you could try is to change your login credentials for your Web Hosting/Server and/or FTP. If that doesn't fix it, I'd recommend contacting the owner of your Web Hosting/Server.
Tip: Try to keep your WordPress version up-to-date. There's new vulnerabilities getting released almost every week or so.
I wouldn't recommend using WordPress at all, but if you are a beginner, it's fine.