Ive searched up soundtrack album for this serie but even on chinese official pages it only shows 5 songs with lyrics. They dıdnt include the varous sountracks which has musıcs wıthout lyrıcs at all :c

This probably means they used it from other serıes or else they would have ınclude ın the album ım sure of it. Why/how im sure of it ? Because ım kınd of obsessed with background musıcs of serıes i watch. Asian american even my own country i used to collect musıc pıeces all the tıme. 

I dislike it the most when they dont ınclude these kınd of stuff ın cerdıts though -_- there were other serıes who dıd this before... Sometımes they even use it from Korean dramas it feels like im watchıng another serıe whenever ı hear songs xD

You are welcome Im here for another rewatch, was checkıng comments and saw your Q. Even though its pretty late I know how frustratıng it is to not being able to fınd a lovely background musıc used ın dramas so i wanted to reply ^^ Sorry that it end up being quite long answer though xD...