How can we be certain of salvation in Christ.
There is simply no objectively correct answer to this question. Various Christian sects believe different things with respect to how we are to gain salvation.
For example, quite recently, Pope Francis, the current Roman Catholic pope, said that people can be saved so long as they act in the correct ways. In this view, we can be saved through our actions. If we act in ways that are pleasing to God we will be saved.
However, many Protestant sects are strongly opposed to this sort of idea. To them, as to Martin Luther, the idea that people can ever be saved through their own efforts is ludicrous. In this view, the only way that we can be saved is to have true faith in Jesus Christ.
To yet other Christians, we can never be certain that we are among the saved. These are people who believe in the idea of predestination. For these people, there is nothing that we can do to accept or reject God’s grace. If we are saved, it is only because God has freely given us that gift. We have nothing to do with our own salvation in this view.
Thus, there are many different visions as to how we can be saved.