i want to know how to do the hydraulic mechanism, and where do i start from
Maybe you can get some ideas here.
Check out the 'sketch blocks' tutorial in the 'advanced techniques' Solidworks tutorials under the 'help' menu. It's a crane instead of a man lift, but the concepts should be easily applied to your project.
Simple, sketched layouts are always a good place to begin, and you can use the layout to evaluate and drive the rest of the design.
thank you very much for your help, much appreciated.