get behind
US /ɡet bɪˈhaɪnd/
UK /ɡet bɪˈhaɪnd/

1.
atrasar, ficar para trás
to fail to make enough progress or to be late with something
:
•
I've got behind with my work.
Eu atrasei meu trabalho.
•
If you miss a few classes, you'll soon get behind.
Se você perder algumas aulas, logo ficará para trás.