Structuring Data for Bidirectional BLE Communication between MCU and Mobile App

Question

I am currently sending data from STM32 to a mobile app using BLE. I use a specific characteristic for the data, which starts with a header containing a CMD. This CMD indicates the type of data being sent. I have only three commands so far. Now, I am unsure about the best practices for sending data back from the app to the STM32:

• Should I use the same characteristic for both directions, or should I use a different one?
• For the CMD in the header, should I create a new set of commands, or can they share the same enum list? For now I have the same list:

typedef enum {
    BLE_P_TYPE_NONE = 0x00,

    // STM32 -> PC
    BLE_P_TYPE_GW_INFO = 0x01,
    BLE_P_TYPE_NODES_INFO = 0x02,

    // PC -> STM32
    BLE_P_TYPE_START_PAIR = 0x80,
    BLE_P_TYPE_STOP_PAIR = 0x81,
    BLE_P_TYPE_DELETE_NODE = 0x82,
    BLE_P_TYPE_NODE_CONTROL = 0x83,

} eBLELinkCharPacketType;

Thank you for your advice!