@Sehb0
To much declines affects your ratings end at some point you will be punished...it is mainly an automated process.
You do not need to decline inquires , just answer the question within the time limit. Regarding booking requests: if the guest did not read the listing or wants something you do not offer, first ask the guest to retract the booking request. If they do, no need to decline.
Also you maybe consider to make the listing more clear, to decrease the amount of "wrong" requests/inquires