Hello
@phrfpeixoto
I see so many people asking questions that have been answered before ... have you tried using the search function to
search within this thread? Or checking the index in post #1 to the wealth of guides and tips?
If you did, you would have found that Casey already wrote some guidelines for updating existing Catalina installations to 10.15.4. You can find it
here.
Edit:
And I can't stress the importance enough: please make a full bootable backup of your system (and test if you can boot it!), as many people experience issues with the update. You can find a link to a guide for making a bootable backup in post
#1 (Going the Extra Mile > Easy Bootable Backup).