I want to know how I can develop GUI applications(32 Bits) without using Delphi language(Object Pascsl), only by using FPC with Lazarus installed(Pascal). Thanks.
Use a widget set directly. Look at e.g. the examples in packages/gtk2 for unix, or the windows win32api usage demo. (demo\win32 in the FPC win32 installation)
But not using lazarus makes you lose platform independance, and a lot of ease.
Looking how lazarus does it, is still a possibility.
A second option is https://github.com/mse-org/mseide-msegui