If the calculated test statistic is 2.148 when the critical value is 2.348, should you reject or not reject the null hypothesis, and explain? you

The approach of critical value is used to determine likely or unlikely through determination whether observed test statistics is more than it would have been if null hypothesis was true. In other words, test statistics is compared to critical value and decision made.
If test statistics is more than critical value, the null hypothesis is rejected. Otherwise, null hypothesis is not rejected.

In the current scenario, test statistics (2.148) is less than critical value (2.348) and thus null hypothesis is not rejected.