Translation:I will practice playing table tennis at school in the afternoon.
This "会" doesn't make sense as referring to skill, so it's not "can" in that sense, and I believe that if the Chinese were referring to ability in the sense of possibility (e.g. fitting into one's schedule), it would more likely use "能" in this context. I think that leaves us with the "will" sense of "会" (with "I'm going to" being a valid alternative). However, I'm open to correction.
As for "pingpong" versus "ping pong", the dictionaries I've checked (Oxford, Merriam-Webster, Cambridge, Australian Oxford, Dictionary.com, Wiktionary) all say that it's spelled with a hyphen or a space in English.
«This afternoon at school I'll practice ping-pong» is correct but was marked wrong. Furthermore, the "Word Bank" has only [practice York at I healthy to the in family school tennis will playing] but lacks AFTERNOON and TABLE. Tsk!
A taller screen reveals the top edges of the missing words but the actual words remain completely obscured, it'd only be possible to guess them by length.
A shame duo fails to afford feedback on such systemic bugs.