Set ps/tt direction

Hi there, i’m really new to font creation, and i have a problem that i can solve.
I generate a font but when i try to use it i find this kind of problem:

As you can see some glyph have a wrong set direction, i had already try to change into ps direction by clicking the button but nothing change.
Can u help me?

P.S. where i can find an exaustive explanation about ps and tt direction, what they are?

P.P.S. i’m really sorry for my bad english, please forgive me!

In Glyphs, take a look at Paths -> Correct Path Direction menu (Shift-Command-R).

There are some details in the “Drawing good paths” tutorial:

and in the Glyphs Handbook: