Does spontaneous process mean the fast process?
A spontaneous process is simply a process that occurs without the need for additional energy. It does not mean that the process will necessarily be a fast process. The process can proceed very slowly. The speed of the process is not a subject of thermodynamics. Thermodynamics only determines if the process is increasing entropy or not. How fast it would be is the subject of kinetics. Thermodynamics even does not know if the process will actually occur or not. It just says it should be.