I googled and found this interesting link on optimizing Joget: Optimizing Joget Platform.

Hi, if you have a very large form that loads in a single request then it might require a lot of processing. Based on the screenshot, the JDBC queries alone also take more than a second. If the form is too heavy, you might want to consider breaking it into smaller pages using a Multi Paged Form, or utilize caching like in Performance Improvement with Userview Caching.

I reduced the form to bare minimum but still taking time to load when click the next button. Moreover, I tried using Multipage which is faster but the problem is it only supports 15 pages. I want to add more than 15.

If you have such a large form with so many pages, you might want to consider restructuring your user interface. Perhaps you could have an entire userview to represent the form, with each menu item representing one page of the form? I would think that is a more practical and user friendly approach, as compared to throwing everything together into one large form.