How to do serialization of Class recursively having members of custom data types in C++?

I want to serialize and deserialize a class Mango . So I have created a function serialize and deserialize respectively.

? serialize(Mango &Man) /// What should be return ?
{
}

    
Mango deserialize(  ?   ) /// What should be function parameter ?
{
}

I don't know how to implement it very efficiently in terms of speed, portability , memory because it contains 10 members of custom data types ( I just mention one but they are all similar) which again are very complex.

I want suggestions for implementation for eg : what should be the return type of serialize function ? vector of bytes ie std::vector<uint8_t> serialize(Mango &Man) ? or should it be nothing like just serializing it into bytes and storing it in memory? or any other way?

Mango Class

class Mango
{
public:
    const MangoType &getMangoType() const { return typeMan; }
    MangoType &getMangoType() { return typeMan; }

private:
    // There are many members of different types : I just mention one.
    MangoType typeMan;
};

Data type classes

//MangoType Class
class MangoType
{
    /// It only has one member ie content
public:
    /// Getter of content vector.

    std::vector<FuntionMango> &getContent() noexcept { return Content; }

private:
    /// \name Data of MangoType.
    
    std::vector<FuntionMango> Content;
    
};


/// FuntionMango class.
class FuntionMango
{
public:
    /// Getter of param types.
    const std::vector<ValType> &getParamTypes() const noexcept
    {
        return ParamTypes;
    }
    std::vector<ValType> &getParamTypes() noexcept { return ParamTypes; }

    /// Getter of return types.
    const std::vector<ValType> &getReturnTypes() const noexcept
    {
        return ReturnTypes;
    }
    std::vector<ValType> &getReturnTypes() noexcept { return ReturnTypes; }

    

private:
    /// \name Data of FuntionMango.
   
    std::vector<ValType> ParamTypes;
    std::vector<ValType> ReturnTypes;

};

//ValType Class
  
enum class ValType : uint8_t
  {
     #define UseValType
     #define Line(NAME, VALUE, STRING) NAME = VALUE
     #undef Line
     #undef UseValType
  };

I want to know the best possible implementation plan in terms of speed and memory for serialize and deserialize functions.

Note : I do not want to transfer it over the network and do not want to use library which requires linking like boost serialization