I've been working with the server only for 2 days so I am sorry if that is simple question. I looked everywhere, but didn't find an answer.
So I have a Google compute engine account and I have owner privileges. When I run
gcloud compute ssh instance --zone us-central1-a
it works, but it creates a key with username that it takes from my computer account.
So when I am in google shell I can add or remove files using sudo. But when I go to Filezilla I have to use ssh file key and username from that key. And the only folder that accessible with that username is it's own folder. I am not sure what is the problem so I gave all the facts I could.
I'm not entirely sure I'm answering the right question, but I'll take a stab at it. The ssh keys created by/used by gcloud are specific to a particular linux user on your VM. As you note, you can use sudo when ssh'd in to edit files/directories owned by different users---the way this works is that you (roughly speaking) temporarily switch users to root when doing the file edit.
An scp client like Filezilla isn't going to be able to switch users that way. So you'll need a different technique to edit files with Filezilla.
I suggest ssh-ing in to your vm and using chmod or chown to change the ownership of files/directories that you want to use with Filezilla. Alternatively you could you use useradd -G to add you username to a group that can edit the files you care about.
Exactly what you'll do depends on the security policy you want to enforce for your files, but there a lots of decent options. The key test to run---can you get to a state where you can edit the files when logged in with SSH, but not using sudo? If so then you should be able to edit the files with Filezilla.