How do I set up a search GREP find all the paragraph beginning, and he will not find manual line breaks?
Don't make manual line breaks, they should be avoided anyway.
Assuming "manual line break" is a Soft (Shift) Return:
This only does a Find. If you want to use this for a replace operation, add a full stop:
and recall it with $1 in the Replace string (as usual). Take care when using it for replacing, as it can mess up the formatting of the first character of your paragraphs.