I am not able to get the values(Systolic, Diastolic and Pulse from a Blood Pressure Measurement machine) after getting all the characteristics of Blood Pressure Service (uuid: 00002a35-0000-1000-8000-00805f9b34fb) and also I am not getting the point about all these characteristics and descriptors. So please, anyone, help me with this issue in BLE device.
You have asked too generic question. May be you need to understand the Android BLE flow from this link.
A GATT database implements one or more profiles(Heart Rate, Audio etc), and each profile is made up of one or more services, and each service is made up of one or more characteristics.
Just to give you glimpse, characteristics are the properties, where you define which one you want to use for read or write.
descriptors are the object on which you write the data to enable/send data.
UUID what you use to send and receive data should be same across client and Server.