Understanding the question being asked

You have to try to take the question at its face value, being sure you look at all its requirements kn detail. So, looking at yojr example:

1
Advise how the mission statement could assist in its performance measurement and management.

The mission statement effectively sets out the organisation’s aims and priorities like “…produce high quality yet affordable goods embodying the latest technology”.

This tells us that quality, price and innovation are key traits or objecfives so the performance measurement and management system must measure and manahe those. To say in your mission tnat innovation is important then not to attempt to measure it, set targets etc is inconsistent.

2
briefly evaluate the relevance of xx companies mission statement.

This requires some knowledge about how mission statements are normally phrased eg usually no figures, state the organisation’s prime activities, state it’s method of competing (eg quality not low price) and usually some generic stuff about values like no discrimination, low ecological impact etc. Therefore, you wojld compare the actual misssion statement against this typical template…..expecting to find areas you could criticise.