“Not allowed to access admin” “redirected” “publishing failed”

I’m getting 3 errors, and trying to fix it, but new errors keep popping up.

1. This page isn’t working ERR_TOO_MANY_REDIRECTS (wp-admin page): this error appeared when i installed it automatically using cpanel so i installed it manually and it worked. But when I edit the url from http to https in Setting this error appears again (I have installed ssl and redirect for https before)
2. Sorry, you are not allowed to access this page: When I add

define(‘FORCE_SSL_ADMIN’, true);
// in some setups HTTP_X_FORWARDED_PROTO might contain
// a comma-separated list e.g. http,https
// so check for https existence
if (strpos($_SERVER[‘HTTP_X_FORWARDED_PROTO’], ‘https’) !== false)
$_SERVER[‘HTTPS’]=’on’;

3. Publishing failed. You are probably offline: I can’t create posts. Default website and also no plugins. I tried a few changes but it still doesn’t work.

I don’t think there are so many errors because I used wordpress 2 years ago and everything was fine at that time. I see quite a few people getting the same errors, I tried following a few tutorials and it still doesn’t work. After fixing this error, the other error reappeared.

Does anyone know how to fix these errors? Thanks everyone!