At the moment, from mobile / smaller screen, you see two button:
[ Write a post ] [ Categories ]
But "categories" can confuse a user if he is currently looking for the link to his profile: he does not expect his profile to be in "categories"; you can expect it, however, if that string were not "categories", but "navigation".
Or, you could do a further button or a further navigation:
[New post] [Categories] Menu
(where Menu = Hamburger menu or the user's thumbnail / avatar)