thanks all. so for the maintenance , I am replacing all of the mention less than once in a year, break pad, freewheel, all of that get bad and I am replacing it frequently .
all other simple maintenance I am doing myself.
about the "bearings need checked " what bearing you mean ? for the wheel? front/rear?BB ?
my question was for something bigger , for example the motor , I think it start to be a bit noisy and I would like to open it and add grease, but I have no idea what type of grease it should be ?