Hi Anh,
Thanks for your very quick respons. Impressed!
Done as you requested, but no result.
See here the title.php that I created like you said.
https://1drv.ms/f/s!AiZg1q2e9vdxhBlxbs_Mz30DdS2c
I have also tried with the same folder structure as for the template, like the Frontend Submission documentation describes.
So I tried with as well as without the folder "template-parts" in the middle.
No effect.