Hello senolsengul,
Thank you for reaching out to our technical support forum. I’m sorry to hear about the trouble you’re experiencing. Rest assured, I will look into this issue for you and work to resolve it as quickly as possible.
The article design is overridden in the template. I have customized this file to fix the second issue:
templates/stratos/html/com_content/article/default.php
Please check the article link.
Also, I could not get the first issue. Please let me know about your first issue in details. What actually you want to do with the header?
Best regards