index.php (or home.php) not used in Twenty fourteen?

Do you have a child theme set up? Do not modify theme files – or all of your changes will be lost when WP is updated.

https://codex.www.ads-software.com/Child_Themes

And BTW, you should get WP updated ASAP – using an outdated version is a security risk.

Thank you for your answer, WPyogi.
Yes, I created a child theme for having the things done correctly. But it doesn’t help. If I put a new index.php on my child theme, it is not used.
I will get my WP updated to 4.1 soon, but I fear that it will one intervene on any way on my current problem…
Best,

See if this plugin helps you sort that file question –

https://www.ads-software.com/plugins/what-the-file/

Great! You saved me.
Wat a useful plugin.
It seems that the only I didn’t check was full-width.php in /page-templates/ folder. And the solution was there.
Thanks again!