跟不上

gēnbushàng
not able to keep up with

CEDICT

Entry Composition

1 跟 gēn
  1. heel
  2. to follow closely
  3. to go with
  4. (of a woman) to marry sb
  5. with
  6. compared with
  7. to
  8. towards
  9. and (joining two nouns)
2 不 bù
  1. no; not so
  2. (bound form) not; un-
3 上 shàng
  1. (bound form) up; upper; above; previous
  2. first (of multiple parts)
  3. to climb; to get onto; to go up
  4. to attend (class or university)
  5. (directional complement) up
  6. (noun suffix) on; above