Learn Turkish: Keşke her çalışan için iş yükü az olsa. - I wish the workload were low for every employee.

The word keşke (I wish / if only) pairs with the conditional suffix -sa / -se to express a present or future wish. By adding -sa to ol- (to be / become), olsa translates to 'were' or 'would be'. It shows we are wishing for a hypothetical situation.

Is çalışan a verb or a noun here?

It acts as a noun meaning 'employee.' It is actually the present participle of çalışmak (to work), formed with the -an suffix. It literally means 'the one who works,' but it is the standard, everyday Turkish word for an employee.

Why is there an -ü at the end of iş yükü?

İş yükü (workload) is a noun compound made of iş (work) and yük (load). In Turkish, when you combine two nouns to create a new specific concept, the second noun must take a possessive suffix. Here, it takes -ü to match the vowel harmony of yük.

Could I drop the word keşke and still mean 'I wish'?

Yes! The conditional suffix -sa on olsa already carries the meaning of a wish all by itself. Adding keşke just adds emotional emphasis (like saying 'if ONLY'), but the sentence is perfectly correct and means the exact same thing without it.