2 Tim 2:
11Here is a trustworthy saying:
If we died with him,
we will also live with him;
12if we endure,
we will also reign with him.
If we disown him,
he will also disown us;
13if we are faithless,
he remains faithful,
for he cannot disown himself.
14Keep reminding God’s people of these things. Warn them before God against quarreling about words; it is of no value, and only ruins those who listen.
15Do your best to present yourself to God as one approved, a worker who does not need to be ashamed and who correctly handles the word of truth.
16Avoid godless chatter, because those who indulge in it will become more and more ungodly.
17Their teaching will spread like gangrene. Among them are Hymenaeus and Philetus,
18who have departed from the truth. They say that the resurrection has already taken place,
and they destroy the faith of some.
19Nevertheless, God’s solid foundation stands firm, sealed with this inscription: “The Lord knows those who are his,” and, “Everyone who confesses the name of the Lord must turn away from wickedness.”
Vs 13.
God never breaks a covenant because He is always faithful. This is not a new thing, we see this throughout the OT. This doesn't cancel Vs 12 which says if we disown Him, He will disown us.
Reading a little further, we see practical example of two people who have fallen from truth (faith) and are causing others to also fall from faith in Christ by what they teach.
You are claiming that once a person has faith in Christ, they are already saved eternally but from the above passage, we see people can indeed fall from faith - does this mean they have lost salvation?
We are also urged to '
do our best' (vs 15). This phrase and all its variants means 'work towards'.