跟不上

not able to keep up with

heel / to follow closely / to go with / (of a woman) to marry sb / with / compared with / to / towards / and (joining two nouns)

no; not so / (bound form) not; un-

used in 上聲|上声[shang3 sheng1]

(bound form) up; upper; above; previous / first (of multiple parts) / to climb; to get onto; to go up / to attend (class or university) / (directional complement) up / (noun suffix) on; above