Can't login, errors prevent it

[RandomFrog]

So for my adopts site I cannot log in, because 3 errors appear at the top of the page. I know my username/password is correct, wrote it down.
I have no experience with coding at all. I've worked on this for a year exactly, and if I can't log in, I'll have to reinstall the site if it can't be fixed.

Here are the errors: (Blocking site name for privacy)

Strict Standards: Declaration of File::getBasename() should be compatible with SplFileInfo::getBasename($suffix = NULL) in /home/-----/public_html/classes/class_file.php on line 19

Warning: session_start(): Cannot send session cookie - headers already sent by (output started at /home/-----/public_html/classes/class_file.php:19) in /home/-----/public_html/classes/class_session.php on line 13

Warning: session_start(): Cannot send session cache limiter - headers already sent (output started at /home/-----/public_html/classes/class_file.php:19) in /home/-----/public_html/classes/class_session.php on line 13

Can I get some help with this?