Hi there,
if you’re using GenerateBlocks, then in the Headline ( button or container ) Blocks -> Typography settings you can manually type in the Font Name, and make sure to NOT check the Google Font API option. Then that block will use your local font.
However, as a general rule, if possible try not to add fonts directly to a block in the editor, or at least keep it to a minimum. Reason for this; if you ever need to change the font you will have to find and edit every block to do so…..
Let us know on that.