en_tn_condensed/2ti/01/12.md

For this cause

"Because I am an apostle"

I also suffer these things

Paul is referring to being a prisoner.

to keep that which I have entrusted to him

Paul is using a metaphor of a person leaving something with another person who is supposed to protect it until he gives it back to the first person. Possible meanings are 1) Paul is trusting Jesus to help him remain faithful, or 2) Paul is trusting that Jesus will ensure that people continue spreading the gospel message. (See: rc://en/ta/man/jit/figs-metaphor)

I am convinced

"I am certain" or "I know for sure"

that day

This refers to the day when God judges all people. (See: rc://en/ta/man/jit/figs-metonymy)