It is hard enough to learn another language without that language playing tricks on you!
English words can be inconsistent in meaning or can vary in pronunciation depending on where in the UK you are from.
Example 1: Same word - different meaning but fortunately different pronunciation.
'Bass' as in 'a type of fish' is universally pronounced with a short 'a' as in 'cat' or 'hat'.
'Bass' as in 'the lowest singing part in a choir' is universally pronounced 'base'.
Example 2: Same word - different meaning but same pronunciation.
'Mass' is universally pronounced with a short 'a' as in 'cat', but can mean 'a Roman Catholic church service', 'a very large number' e.g of people and also 'a body of matter' as measured in kilograms.
Example 3: Same word - same meaning but different pronunciation.
So how do you say 'Class' ? In Ann's native county of Lancashire in northern UK it would be with a short 'a' as in 'cat' and 'mass'. In Cambridge in southern UK the 'a' would be as in ''car' or 'aunt' or, more directly, it rhymes with a slang term for that part of your body on which you sit !