The following situation sees a 'foreign' nurse meet the ward sister for the first time. The situation takes an interview form, where the ward nurse wants to see if the 'new' nurse is ready and capable to start work.
A number of questions are asked, both by the ward sister and the nurse.
The nurse asks the question: "It is always harder, understanding and speaking to children, as opposed to adults, isn't it?" Note the use of the tag question "isn't it". This is used at the end of a statement when the speaker would like confirmation of that statement. Tag questions are used in English to make what we say sound less aggressive.
Note the use of the past simple tense when the ward nurse says: "I see you completed the three-day Hospital Induction Course last week." "Completed" is used rather than "have completed". In this example the time when the action finished is indicated, thus the past simple tense is used.