简直 (simply / literally — exaggeration)

"Simply unbelievable!"

• simply简直jiǎn zhí = "simply / literally / just" — an exaggeration booster.
• this这zhèsimply简直jiǎn zhívery good太好了tài hǎo le！ = "this is simply wonderful!"
• It says reality is so extreme it's almost beyond words.

simply简直jiǎn zhí + (extreme statement)

• simply简直jiǎn zhí ramps a description up to "you won't believe it".

this这zhèsimply简直jiǎn zhítoo太tàigreat棒bàng了le！

• simply简直jiǎn zhí太棒了tài bàng le = "it's simply amazing!"

Recap

Read the full reference: HSK 5 grammar — Adverbs.