Hey @christian thanks for your reply.
Regarding translation, I did everything written at https://theme.co/docs/theme-translations and now I have “Hepsi” instead of “All” thanks a lot.
Regarding portfolio page layout problem, under theme options > blog > style > masonry fixes this a bit, but the column number can’t be more than three (even though I have options up to four for the first portfolio page), so there’s again a layout change which is directly related to the theme, not my customisations. I’m leaving the style option as masonry for you to see it.
Secondly, second page assumes I have 10 posts in first page, so it displays posts starting from 11th. This is another bug of the theme, because I set it 12 posts per page at the portfolio page setup. // EDIT: Fixed this by a setting from JetPack plugin. Though, I shouldn’t need a plugin to fix this.
But my problem with the page title (“Projelerimiz” on page 1 and “Portfolio I Sayfa 2” on page 2) still exists. This is another problem with the theme.