Lizbeth1, your post had nothing to do with Pamac so i've deleted it. Note the difference: Pamac vs Pacman (and even if this was a thread about Pacman, it still wouldn't be the appropriate place for your post. Your problem is related to package signatures issues when you try to update). Make yourself a new thread asking for help with your problem.
Also, the first result of a Google search for 'manjaro signature problems' probably has your solution.