something is totally wrong with this sentence
Please explain why, if I may ask.
The sentence in itself (can’t tell for the translation) is correct, it means:
“You should be able to walk in a couple of days.”
(could be heard when someone is sick and wonders when he recovers)
être en mesure de faire [qch] is an expression that means "“be in a position to do [sth], be able to do [sth]”