how..

[yaxiiah]

how i may edit (gal name)/themes...i've seen another galleries that had deleted templates... and how i may change some of the actual templates

[Joachim Müller]

how i may edit (gal name)/themes...i've seen another galleries that had deleted templates...

Go ahead and remove surplus themes you don't need any longer by deleting the corresponding folders using your FTP app.

and how i may change some of the actual templates

Use a plain text editor to edit the files within the theme folder you want to see changed.