Learn Farsi: نه، این محفظه هیچ خسته‌کننده نیست.

This is the adverbial use of hich. Instead of meaning 'no [noun]', placing it independently before a predicate adjective or adverb with a negative verb changes its meaning to 'not at all'. So, hich khasteh-konandeh nist means 'is not boring at all'.

Could I use aslan instead of hich in this sentence?

Yes, you could say aslan khasteh-konandeh nist and it would mean the exact same thing. Using hich in this adverbial way is simply another common, sometimes slightly more emphatic option to express absolute negation.

I know khasteh means 'tired'. How does khasteh-konandeh become 'boring'?

The suffix -konandeh acts like the English '-ing' or '-er', turning a verb into an active participle (the thing doing the action). Since it comes from the compound verb khasteh kardan (to tire or to bore), khasteh-konandeh literally means 'tiring-maker', which is how Farsi expresses 'boring' or 'tiring'.

What kind of object is a mahfazeh?

mahfazeh refers to an enclosure, casing, container, or chamber. It shares an Arabic root with words related to protecting or keeping, such as hefz. You will often see it used for things like a glass display case, a machine's protective housing, or a scientific testing chamber.