Reduce Header size, title, and on blog page only

I have searched the forum for a previous post with no luck.
On the blog page, the header block size is too large for me. I would like to reduce it down to 150px however when I paste the code into the additional CSS area the text from the <h2> tag and <p> tags remain in the same place and lay over the beginning of the blog text. Please help.

Hi there

Hope you are having a good day and thank you for your question
In order to check your question i need to see your live website, please provide url and i will take a look