In other men’s labours (en allotriois kopois). Allotrios means belonging to another as in Luk 16:12. Paul founded the church in Corinth.
As your faith groweth (auxanomenēs tēs pisteōs). Genitive absolute of the present passive participle of auxanō, to grow.
We shall be magnified (megalunthēnai). First aorist passive infinitive of megalunō, old verb (Luk 1:46) to make great (cf. Phi 1:20 of Christ). Indirect discourse after elpida (hope) with the construction of elpizō, to hope.